阅读说明：本技术 烧结体、粉末及其制造方法 (Sintered body, powder, and method for producing same ) 是由 松井光二 细井浩平 于 2020-04-06 设计创作，主要内容包括：本发明提供一种用于通过常压烧结得到通过SEPB法测定的破坏韧性值高的氧化锆烧结体的原料、由该原料得到的烧结体、及其制造方法中的至少任一者。所述烧结体的特征在于,包含含有稳定化剂的氧化锆,单斜晶率为0.5％以上。这样的烧结体优选通过具有以下特征的制造方法而得到：使用以包含含有稳定化剂且单斜晶率大于70％的氧化锆、且单斜晶氧化锆的晶粒粒径为大于23nm且80nm以下为特征的粉末。(The present invention provides a raw material for obtaining a zirconia sintered body having a high fracture toughness value measured by an SEPB method by atmospheric pressure sintering, a sintered body obtained from the raw material, and at least any one of the production methods thereof. The sintered body is characterized by containing zirconia containing a stabilizer and having a monoclinic ratio of 0.5% or more. Such a sintered body is preferably obtained by a production method having the following features: a powder is used which comprises zirconia containing a stabilizer and having a monoclinic rate of more than 70% and is characterized in that the grain size of the monoclinic zirconia is more than 23nm and 80nm or less.)

1. A sintered body comprising zirconia containing a stabilizer, characterized in that the monoclinic ratio is 0.5% or more.

2. The sintered body according to claim 1, wherein a ratio of an integrated intensity of an XRD peak corresponding to the (11-1) plane of monoclinic zirconia to an XRD peak corresponding to the (111) plane of monoclinic zirconia is 0 or more.

3. The sintered body according to claim 1 or 2, wherein the stabilizer is 1 or more selected from yttrium oxide, calcium oxide, magnesium oxide, and cerium oxide.

4. The sintered body according to any one of claims 1 to 3, wherein the content of the stabilizer is 1.0 mol% or more and less than 2.5 mol%.

5. The sintered body according to any one of claims 1 to 4, wherein a fracture toughness value measured by a method according to the SEPB method specified in JIS R1607 is 6 MPa-m^0.5Above and 11MPa m^0.5The following.

6. The sintered body according to any one of claims 1 to 5, wherein the sintered body contains 1 or more additive components selected from alumina, germania, and silica.

7. The sintered body according to any one of claims 1 to 6, wherein the additive component is alumina.

8. The sintered body according to any one of claims 1 to 7, wherein the zirconia comprises monoclinic zirconia and at least any one selected from tetragonal zirconia and cubic zirconia.

9. The sintered body according to any one of claims 1 to 8, wherein a ratio of a tetragonal crystal rate of the sintered body after immersion treatment in hot water at 140 ℃ for 6 hours to a tetragonal crystal rate of the sintered body before immersion treatment in hot water at 140 ℃ for 6 hours is 15% or more.

10. The method for producing a sintered body according to any one of claims 1 to 9, wherein a powder is used, which is characterized by containing zirconia containing a stabilizer and having a monoclinic rate of more than 70%, and by having a grain size of monoclinic zirconia of more than 23nm and 80nm or less.

11. A powder comprising zirconia containing a stabilizer and having a monoclinic ratio of more than 70%, wherein the monoclinic zirconia has a crystal grain diameter of more than 23nm and 80nm or less.

12. The powder of claim 11, wherein the crystalline phase of zirconia comprises monoclinic zirconia and tetragonal zirconia.

13. The powder according to claim 11 or 12, wherein the stabilizer is 1 or more selected from the group consisting of yttrium oxide, calcium oxide, magnesium oxide, and cerium oxide.

14. The powder according to any one of claims 11 to 13, wherein the content of the stabilizer is 1.0 mol% or more and less than 2.5 mol%.

15. The powder according to any one of claims 11 to 14, wherein the powder comprises 1 or more additional components selected from alumina, germania and silica.

16. The powder according to claim 15, wherein a content of the additive component is 0.1% by mass or more and 30% by mass or less.

17. The powder according to any one of claims 11 to 16, wherein the powder has a BET specific surface area of 6m²More than or equal to g and less than 20m²/g。

18. The powder according to any one of claims 11 to 17, wherein the median particle diameter of the powder is 0.05 μm or more and 0.3 μm or less.

19. A part comprising the sintered body of any one of claims 1 to 9.

Technical Field

The present disclosure relates to a sintered body having zirconia as a main phase, a powder as a raw material thereof, and a method for producing the same.

Background

The zirconia sintered body has been studied for use in decorative applications such as decorative parts for watches, portable electronic devices, automobiles, home appliances, and the like, in addition to conventional applications requiring strength as a grinding medium, a structural material, and the like. Sintered bodies for decorative applications are required to have reduced brittleness, i.e., to have an improved fracture toughness value.

Heretofore, various zirconia sintered bodies have been reported for the purpose of improving fracture toughness values. For example, patent document 1 reports a zirconia-alumina composite sintered body obtained by mixing a commercially available zirconia powder containing 3 mol% yttria, which is produced by a neutralization coprecipitation method, with a commercially available alumina powder to prepare a mixed powder, and microwave sintering the mixed powder. The fracture toughness value (K) of the composite sintered body measured by IF method is described_IC) Is 6.02 to 6.90 MPa.m^1/2。

Patent document 2 reports a zirconia sintered body obtained by subjecting a zirconia powder containing phosphorus, silica, and alumina to Hot Isostatic Pressing (HIP). It is described that the sintered body has a fracture toughness value of 6 to 11MPa m measured by a method prescribed in JIS R1607^1/2。

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2017-226555

Patent document 2: japanese patent application laid-open publication No. 2011-178610

Disclosure of Invention

Technical problem to be solved by the invention

The zirconia sintered bodies disclosed in patent documents 1 and 2 need to be produced by applying a special sintering method such as microwave sintering and HIP treatment, and thus are difficult to apply industrially. However, when applied to decorative parts, it is also required to evaluate the brittleness of the sintered body with a fracture toughness value having high reliability. In contrast, even if the fracture toughness is measured by a standardized method, there are a plurality of methods, and the value obtained by each measurement method greatly differs. While the fracture toughness value of patent document 1 is a value measured by a simple method, the method of measuring the fracture toughness value of patent document 2 is not clear per se, and the reliability of the values disclosed in both is low.

An object of the present disclosure is to provide at least one of a raw material for obtaining a zirconia sintered body having a high fracture toughness value measured by an SEPB method by atmospheric pressure sintering, a sintered body obtained from the raw material, and a method for producing the same.

Means for solving the problems

The gist of the present disclosure is as follows.

[1] A sintered body comprising zirconia containing a stabilizer, characterized in that the monoclinic ratio is 0.5% or more.

[2] The sintered body according to the above [1], wherein a ratio of an integrated intensity of an XRD peak corresponding to the (11-1) plane of monoclinic zirconia to an integrated intensity of an XRD peak corresponding to the (111) plane of monoclinic zirconia is 0 or more.

[3] The sintered body according to the above [1] or [2], wherein the stabilizer is 1 or more selected from yttrium oxide, calcium oxide, magnesium oxide, and cerium oxide.

[4] The sintered body according to any one of the above [1] to [3], wherein a content of the stabilizer is 1.0 mol% or more and less than 2.5 mol%.

[5]According to the above [1]To [4]]The sintered body according to any one of the above methods, wherein the sintered body is measured by a method according to the SEPB method defined in JIS R1607A definite fracture toughness value of 6 MPa-m^0.5Above and 11MPa m^0.5The following.

[6] The sintered body according to any one of the above [1] to [5], which contains 1 or more additive components selected from alumina, germania and silica.

[7] The sintered body according to any one of the above [1] to [6], wherein the additive component is alumina.

[8] The sintered body according to any one of the above [1] to [7], wherein the zirconia includes monoclinic zirconia and at least any one selected from tetragonal zirconia and cubic zirconia.

[9] The sintered body according to any one of the above [1] to [8], wherein a ratio of a tetragonal crystal rate after immersion treatment in hot water at 140 ℃ for 6 hours to a tetragonal crystal rate before immersion treatment in hot water at 140 ℃ for 6 hours is 15% or more.

[10] The method for producing a sintered body according to any one of the above [1] to [9], characterized by using a powder containing zirconia containing a stabilizer and having a monoclinic ratio of more than 70% and having a grain size of the monoclinic zirconia of more than 23nm and 80nm or less.

[11] A powder comprising zirconia containing a stabilizer and having a monoclinic ratio of more than 70%, wherein the monoclinic zirconia has a crystal grain diameter of more than 23nm and 80nm or less.

[12] The powder according to [11] above, wherein the crystal phase of the zirconia comprises monoclinic zirconia and tetragonal zirconia.

[13] The powder according to the above [11] or [12], wherein the stabilizer is 1 or more selected from the group consisting of yttrium oxide, calcium oxide, magnesium oxide and cerium oxide.

[14] The powder according to any one of [11] to [13] above, wherein a content of the stabilizer is 1.0 mol% or more and less than 2.5 mol%.

[15] The powder according to any one of the above [11] to [14], which comprises 1 or more additional components selected from alumina, germania and silica.

[16] The powder according to [15], wherein a content of the additive component is 0.1% by mass or more and 30% by mass or less.

[17]According to the above [11]]To [16]]The powder according to any one of the above, wherein the BET specific surface area is 6m²More than or equal to g and less than 20m²/g。

[18] The powder according to any one of [11] to [17] above, wherein the median particle diameter is 0.05 μm or more and 0.3 μm or less.

[19] A member comprising the sintered body of any one of the above [1] to [9 ].

ADVANTAGEOUS EFFECTS OF INVENTION

The present disclosure can provide at least one of a raw material for obtaining a zirconia sintered body having a high fracture toughness value measured by an SEPB method by atmospheric pressure sintering, a sintered body obtained from the raw material, and a method for producing the same.

Detailed Description

Hereinafter, the present disclosure will be described by illustrating an example of an embodiment.

The terms in the present embodiment are as follows.

The "monoclinic ratio" and the "tetragonal ratio" refer to the proportions of monoclinic zirconia and tetragonal zirconia, respectively, in the crystal phase of zirconia. Further, the "monoclinic intensity ratio" is a ratio of the integrated intensity of an XRD peak corresponding to the (11-1) plane of monoclinic zirconia in the crystal phase of zirconia to the integrated intensity of an XRD peak corresponding to the (111) plane of monoclinic zirconia.

The monoclinic ratio can be obtained from the following formula (1), the tetragonal ratio can be obtained from the following formula (2), and the monoclinic intensity ratio can be obtained from the following formula (3) by using the powder X-ray diffraction (hereinafter also referred to as "XRD") spectrum of the powder, and by using the surface XRD spectrum of the sintered body after mirror polishing.

f_m＝{I_m(111)+I_m(11-1)}/[I_m(111)+I_m(11-1)+I_t(111)+I_c(111)]×100 (1)

f_t＝I_t(111)/[I_m(111)+I_m(11-1)+I_t(111)+I_c(111)]×100 (2)

M_(11-1)/(111)＝{I_m(11-1)/I_m(111)} (3)

In formulae (1) to (3), f_mIs monoclinic ratio (%), f_tIs the tetragonal crystal ratio (%), M_(11-1)/(111)Is the monoclinic strength ratio, I_m(111) And I_m(11-1) is the integrated intensity of XRD peaks corresponding to the (111) plane and the (11-1) plane of monoclinic zirconia, respectively, I_t(111) Is the integrated intensity of the XRD peak corresponding to the (111) plane of tetragonal zirconia, and I_c(111) Is the integrated intensity of the XRD peak corresponding to the (111) plane of the cubic zirconia.

The XRD spectrum may be measured under the following conditions.

Ray source: cu Ka line (λ 0.15418nm)

Measurement mode: continuous scanning

Scanning speed: 4 °/min

Step length: 0.02 degree

Measurement range: 2 theta is 26-33 DEG

In the XRD spectrum measurement, the XRD peak corresponding to each crystal plane of zirconia is preferably measured as a peak having a peak position at 2 θ below.

XRD peak corresponding to (111) plane of monoclinic zirconia: 2 theta is 31 + -0.5 DEG

XRD peak corresponding to (11-1) plane of monoclinic zirconia: 2 theta 28 +/-0.5 DEG

The RD peaks corresponding to the (111) planes of tetragonal zirconia and cubic zirconia were repeatedly measured, and 2 θ at the peak positions was 30 ± 0.5 °.

The integrated intensity of XRD peaks for each crystal plane can be determined by separating each XRD peak by the method described in H.Toraya, J.appl.Crystallogr.19, 440-447(1986) using "PRO-FIT" as a calculation program.

The sintered body after surface polishing for XRD measurement was obtained in a state in which the surface roughness Ra of the measurement surface was 0.04 μm or less by performing automatic polishing with sandpaper, automatic polishing with diamond slurry having an average particle size of 3 μm, and automatic polishing with colloidal silica having an average particle size of 0.03 μm in this order after cutting the surface after sintering with a flat grinding disk.

"grain size of monoclinic zirconia" (hereinafter also referred to as "D")_m") is a value determined from the XRD spectrum of the powder using the following formula (4)," crystal grain size of tetragonal zirconia "(hereinafter also referred to as" D_t") is a value determined from the XRD spectrum of the powder using the following formula (5).

D_m＝κλ/(βcosθ_m) (4)

D_t＝κλ/(βcosθ_t) (5)

In formulae (4) and (5), D_mIs the grain size (nm), D, of monoclinic zirconia_tThe crystal grain size (nm) of tetragonal zirconia, κ is the Scherrer constant (κ ═ 1), λ is the wavelength (nm) of the light source used in the XRD measurement, and β is the full width at half maximum (°) θ, corrected for the spread of the instrument using quartz sand (manufactured by wako pure chemical industries) with the grain size adjusted to 25 to 90 μm_mIs the Bragg angle (. degree.) and theta.corresponding to the (11-1) plane of monoclinic zirconia in XRD measurement_tIs the bragg angle (°) of reflection corresponding to the (111) plane of tetragonal zirconia in XRD measurement. When CuK α line was used as a light source for XRD measurement, λ was 0.15418 nm.

The "BET specific surface area" is measured by adding nitrogen gas (N) in accordance with JIS R1626-₂) The value obtained by the BET method 1 point method of the adsorbed substance.

The "particle diameter based on volume distribution" refers to the particle diameter of the powder obtained by volume particle diameter distribution measurement by a laser diffraction method. The particle diameter obtained by the laser diffraction method is a diameter approximate to a non-spherical shape. The following conditions may be mentioned as conditions for measuring the volume particle size distribution.

Measurement of the sample: powder slurry

Refractive index of zirconia: 2.17

Refractive index of solvent (water): 1.333

Measuring time: 30 seconds

Pretreatment: ultrasonic dispersion treatment

The "median particle diameter" refers to a particle diameter corresponding to 50% by volume of a cumulative volume particle diameter distribution curve obtained by volume particle diameter distribution measurement by a laser diffraction method.

The "particle size distribution curve" refers to a curve showing the particle size distribution of the powder obtained by the volume particle size distribution measurement by the laser diffraction method.

The "fracture toughness value" is a value of fracture toughness (MPa. m) measured by a method according to the SEPB method prescribed in JIS R1607^0.5). The fracture toughness value may be measured by using a pillar-shaped sintered body sample having a width of 4mm and a thickness of 3mm by using an inter-fulcrum distance of 30mm, and an average value of 10 measurements may be used as the fracture toughness value of the sintered body of the present embodiment. In JIS R1607, two types of fracture toughness measurements, i.e., the IF method and the SEPB method, are specified. The IF method tends to have a larger measured value than the SEPB method. Further, IF method is a simple measurement method, and thus the measurement value fluctuates greatly every measurement. Therefore, the fracture toughness value in the present embodiment cannot be compared with the fracture toughness value measured by the IF method in terms of absolute value. Similarly, the fracture toughness value measured by a method other than the SEPB method and the fracture toughness value measured by the SEPB method cannot be compared in absolute value.

"bending strength" means a value of three-point bending strength obtained by a three-point bending test according to JIS R1601. The bending strength was measured using a pillar-shaped sintered body sample having a width of 4mm and a thickness of 3mm by using an inter-fulcrum distance of 30mm, and an average value of 10 measurements was used as the bending strength of the sintered body of the present embodiment.

"Total light transmittance" means the total light transmittance to light having a wavelength of 600nm at a sample thickness of 1.0mm, and can be measured by a method in accordance with JIS K7361. The light having a wavelength of 600nm can be used as the incident light, and can be obtained as a transmittance value obtained by summing the diffuse transmittance and the linear transmittance of the incident light. A sample having a thickness of 1mm and a surface roughness (Ra) of both surfaces (the measurement surface and the surface opposite to the measurement surface) of 0.02 μm or less may be used as a measurement sample, and the sample is irradiated with light having a wavelength of 600nm using a conventional spectrophotometer (for example, V-650, manufactured by JASCO corporation) and the transmitted light is condensed by an integrating sphere to measure the transmittance (diffuse transmittance and linear transmittance) of the sample, and the transmittance may be regarded as the total light transmittance.

"Linear transmittance" means the total light transmittance at a wavelength of 600nm when the sample thickness is 0.05mm or more and 0.2mm or less, preferably 0.05mm or more and 0.15mm or less, particularly 0.09mm, and can be measured by the method according to JIS K7361. Light having a wavelength of 600nm can be used as incident light, and the value of the linear transmittance for the incident light can be determined. A sample having a thickness of 1mm and a surface roughness (Ra) of both surfaces (the measurement surface and the reverse surface to the measurement surface) of 0.02 μm or less may be used as a measurement sample, and the sample is irradiated with light having a wavelength of 600nm using a conventional spectrophotometer (for example, V-650, manufactured by JASCO corporation) and the transmitted light is condensed by an integrating sphere to measure the linear transmittance of the sample.

"relative density" refers to the ratio (%) of the measured density to the theoretical density. The measured density of the molded article is a volume ratio (g/cm) determined by a dimension measurement with respect to a mass measured by a mass measurement³) The measured density of the sintered body is a volume ratio (g/cm) measured by the Archimedes method with respect to the mass measured by mass measurement³) The theoretical density is a density (g/cm) determined by the following formulas (6) to (9)³)。

A＝0.5080+0.06980X/(100+X) (6)

C＝0.5195-0.06180X/(100+X) (7)

ρ_Z＝[124.25(100-X)+225.81X]/[150.5(100+X)A²C] (8)

ρ₀＝100/[(Y_A/3.987)+(Y_G/3.637)+(Y_S/2.2)+(100-Y_A-Y_G-Y_S)/ρ_Z] (9)

In the formulae (6) to (9), ρ₀Is the theoretical density, p_ZIs the theoretical density of zirconia, A and C are constants, and X is yttria relative to zirconia (ZrO)₂) And yttrium oxide (Y)₂O₃) The molar ratio (% by mol) of the total of (A), (B), (C), (D) and (D)_A、Y_GAnd Y_SMeans Al in terms of the formed or sintered body₂O₃Aluminum oxide of (2), converted to GeO₂And conversion to SiO₂Relative to the amount of silicon dioxide (A) converted to ZrO, respectively₂、Y₂O₃、Al₂O₃、GeO₂And SiO₂The mass ratio (% by mass) of the total of zirconia, yttria, alumina, germania and silica.

The sintered body of the present embodiment will be described below.

The present embodiment is a sintered body containing zirconia containing a stabilizer, and having a monoclinic ratio of 0.5% or more.

The sintered body of the present embodiment is a sintered body containing zirconia containing a stabilizer, and is a sintered body having zirconia containing a stabilizer as a main phase, that is, a so-called zirconia sintered body.

The stabilizer has a function of stabilizing zirconia, and examples thereof include those selected from the group consisting of calcium oxide (CaO), magnesium oxide (MgO), and cerium oxide (CeO)₂) And yttrium oxide (Y)₂O₃) Preferably at least one of cerium oxide and yttrium oxide, and more preferably yttrium oxide. In the sintered body of the present embodiment, the content of the stabilizer may be a content that can partially stabilize zirconia. The content of the stabilizer is, for example, in the case where the stabilizer is yttria, the content of yttria relative to zirconia (ZrO) in the sintered body₂) And yttrium oxide (Y)₂O₃) (iii) total molar ratio of (2) ({ Y)₂O₃/(ZrO₂+Y₂O₃)}×100[mol％](ii) a Hereinafter, also referred to as "yttrium oxide content"), it is possible to exemplify 1.0 mol% or more and 2.5 mol% or less, further 1.1 mol% or more and 2.2 mol% or less, further 1.1 mol% or more and 2.0 mol% or less, preferably 1.2 mol% or more and less than 2.0 mol%, more preferably 1.2 mol% or more and 1.8 mol% or less. When the content of the stabilizer is within the above range, the fracture toughness value measured by the SEPB method tends to be high. The content of yttrium oxide is preferably 1.4 mol% or more and 2.1mol% or less, further 1.5 mol% or more and 1.8 mol% or less.

The stabilizer is preferably solid-dissolved in zirconia, and the sintered body of the present embodiment preferably contains no undissolved stabilizer, and the stabilizer is entirely solid-dissolved in zirconia, and more preferably does not have an XRD peak of the stabilizer in an XRD spectrum of the sintered body of the present embodiment. In the present embodiment, when an XRD peak, which is a stabilizer not belonging to an XRD peak of zirconia, can be confirmed, it can be considered that the stabilizer contains an undissolved stabilizer.

The sintered body of the present embodiment may contain alumina (Al)₂O₃) Germanium oxide (GeO)₂) And silicon dioxide (SiO)₂) 1 or more of the above-mentioned additives. The additive component is preferably at least one of alumina and germanium oxide, and more preferably alumina. By including the additive component, the grain boundary strength between grains is easily increased even when the content of the stabilizer for zirconia is small. When the additive component is contained, the sintered body of the present embodiment is a sintered body containing the additive component and the rest of zirconia containing a stabilizer. The content of the additive component is a mass ratio of the additive component of the sintered body to the total mass of the zirconia, the yttria and the additive component. For example, in the case of a sintered body of zirconia containing alumina as an additive component and yttria as a remainder, the { Al (Al) } is passed₂O₃/(ZrO₂+Y₂O₃+Al₂O₃) }X100 [ mass%]) And then the result is obtained. The content of the additive component may be 0.05% by mass or more and 30% by mass or less, preferably more than 0.1% by mass and 25% by mass or less, and more preferably 0.2% by mass or more and 20% by mass or less. If the content of the additive component is 0.02 mass% or more and 0.3 mass% or less, the mechanical strength tends to be high, and the transformation into monoclinic zirconia tends to be difficult to occur.

The sintered body of the present embodiment preferably contains no substances other than inevitable impurities. As the inevitable impurities, hafnium oxide (HfO) may be exemplified₂)。

The monoclinic ratio of the sintered body of the present embodiment is 0.5% or more, preferably 0.5% or more and 15% or less, and more preferably 0.8% or more and 12% or less. When the monoclinic ratio is any one of 1% or more and 15% or less, 2% or more and 14% or less, 5% or more and 12% or less, and 7% or more and 11% or less, fracture toughness tends to be high, and therefore, it is preferable. On the other hand, when the monoclinic ratio is 0.5% or more and 5% or less, more preferably 0.8% or more and 3% or less, the flexural strength tends to be high, and therefore, it is preferable.

The as-sintered-surface (hereinafter also referred to as "sintered surface") immediately after sintering is rough and contains a large number of sources of damage such as unevenness. In order to prevent the sintered body from being broken, the sintered body was polished by removing the sintered surface by machining such as grinding before being used for evaluation and various applications, thereby exposing a mirror-surface (hereinafter also referred to as "mirror surface"). The mirror surface is a smooth surface, and a surface with Ra 0.04 μm can be exemplified. The monoclinic ratio is a value in the mirror surface of the sintered body. A conventional sintered body having partially stabilized zirconia as a main phase contains at least either tetragonal zirconia or cubic zirconia in its crystal phase after mirror processing such as processing or polishing, and substantially contains no monoclinic zirconia or contains little monoclinic zirconia. Further, the sintered body having low mechanical properties is broken in mirror processing, and the measurement sample cannot be processed, and there is a possibility that the monoclinic ratio cannot be measured. In contrast, the sintered body of the present embodiment has monoclinic zirconia satisfying the monoclinic ratio described above in the mirror surface thereof. Therefore, the sintered body of the present embodiment can be considered to be a sintered body having monoclinic zirconia in the entire sintered body or a sintered body containing tetragonal zirconia in which phase transformation to monoclinic zirconia easily occurs.

In the sintered body of the present embodiment, zirconia includes monoclinic zirconia and at least one selected from tetragonal zirconia and cubic zirconia, and preferably includes monoclinic zirconia and tetragonal zirconia.

The monoclinic zirconia contained in the sintered body of the present embodiment has at least monoclinic crystals in its XRD spectrumMonoclinic zirconia having XRD peaks corresponding to the zirconia (111) plane. When the monoclinic zirconia is included in a state before the deterioration treatment, the sintered body tends to have a high fracture toughness value and to be less likely to undergo hydrothermal deterioration. In the case where monoclinic zirconia is produced by deterioration of the sintered body, the intensity of the XRD peak corresponding mainly to the monoclinic zirconia (11-1) plane in the XRD spectrum becomes strong. On the other hand, the monoclinic zirconia contained in the sintered body of the present embodiment preferably has at least an XRD peak corresponding to the (111) plane of the monoclinic zirconia in its XRD spectrum, and the monoclinic intensity ratio thereof is preferably 0 or more, more preferably 0.3 or more, further preferably 0.4 or more, and further more preferably 0.5 or more. The monoclinic strength ratio is preferably 10 or less, 8 or less, 5 or less, 3 or less, and 1.5 or less, and may be 1.2 or less, and further 1.0 or less. The monoclinic strength ratio was determined by equation (3). Thus, in I_m(111) In the sintered body having no monoclinic zirconia (111) plane, that is, having no XRD peak, the monoclinic intensity ratio is infinite, and thus cannot be obtained. That is, the sintered body of the present embodiment preferably does not include a sintered body having an infinite monoclinic strength ratio.

The average crystal grain size of the crystal grains of zirconia in the sintered body of the present embodiment varies depending on the sintering temperature, and examples thereof include any of 0.1 μm to 0.8 μm, 0.15 μm to 0.60 μm, 0.20 μm to 0.55 μm, and 0.25 μm to 0.45 μm.

The relative density of the sintered body of the present embodiment (hereinafter also referred to as "sintered body density") is preferably 98% or more and 100% or less, more preferably 98.4% or more and 100% or less, and still more preferably 99% or more and 100% or less.

Further, the sintered body of the present embodiment is preferably a sintered body obtained by atmospheric sintering (so-called atmospheric sintered body), more preferably a sintered body obtained by atmospheric sintering in an atmospheric atmosphere. Further, it is preferable that the sintering treatment other than the atmospheric sintering is not performed, and more preferably, the sintering treatment after the atmospheric sintering is not performed. As the sintering treatment other than the atmospheric pressure sintering, 1 or more kinds selected from the group consisting of pressure sintering, vacuum sintering and microwave sintering can be exemplified.

The fracture toughness value (fracture toughness value measured by the method according to the SEPB method defined in JIS R1607) of the sintered body of the present embodiment can be, for example, 6MPa · m^0.5Above and 11MPa m^0.5Hereinafter, it is preferably 6.2MPa · m^0.5More preferably 7MPa m or more^0.5More preferably 8MPa m^0.5The above. The fracture toughness value is preferably high, and examples thereof include 11MPa · m^0.5The lower, further 10.5MPa · m^0.5The lower, still more 9.5MPa · m^0.5The lower, still further 9MPa m^0.5The lower, still more 8.5MPa · m^0.5The following. By having such a fracture toughness value, it is easy to process a sintered body having a thickness of, for example, 1mm or less, and further having a thickness of 0.5mm or less. Thus, the sintered body of the present embodiment may be a sintered body having a sintered body thickness of 0.05mm to 0.3mm, or a sintered body having a sintered body thickness of 0.08mm to 0.25 mm.

The sintered body of the present embodiment can be exemplified by a sintered body having a flexural strength of 1000MPa or more and 1550MPa or less, further 1100MPa or more and 1500MPa or less, preferably 1100MPa or more and 1460MPa or less, and more preferably 1200MPa or more and 1400MPa or less.

The sintered body of the present embodiment preferably has a total light transmittance of 20% or more and 50% or less, more preferably 25% or more and 45% or less, and still more preferably 30% or more and 40% or less. In particular, when the additive component is more than 0% by mass and 25% by mass or less, further 0.2% by mass or more and 5% by mass or less, and further 0.23% by mass or more and 3% by mass or less, the total light transmittance is preferably 20% or more and 45% or less, further 25% or more and 40% or less.

The sintered body of the present embodiment can be exemplified by one having a linear transmittance of 1% or more and 20% or less, 1% or more and 15% or less, 1% or more and 10% or less. The linear transmittance is a value measured for a sintered body having a sample thickness of 0.05mm to 0.2mm, preferably 0.05mm to 0.15mm, and particularly 0.09 mm. The linear transmittance in the present embodiment is a measured value at such a sample thickness, and is different from an estimated value or a calculated value obtained from a linear transmittance measured with a thicker sintered body such as a sintered body having a sample thickness of 0.5mm or more.

The sintered body of the present embodiment particularly preferably has any one of a linear transmittance of 1% or more and 10% or less, 1.5% or more and 8% or less, 2% or more and 7.5% or less, and 2.5% or more and 7.3% or less when the sample thickness is 0.09 mm.

The tetragonal zirconia contained in the sintered body of the present embodiment is preferably less likely to undergo a phase transition to monoclinic zirconia by hydrothermal treatment (hereinafter also referred to as "hydrothermal degradation"), and the ratio of the tetragonal crystal rate after immersion treatment in hot water at 140 ℃ for 6 hours to the tetragonal crystal rate before immersion treatment in hot water at 140 ℃ for 6 hours (hereinafter also referred to as "residual tetragonal crystal rate" or "Δ T%") is preferably 15% or more, more preferably 70% or more, and still more preferably 80% or more. When the tetragonal zirconia is not transformed into monoclinic zirconia by immersion treatment in hot water at 140 ℃ for 6 hours, the residual tetragonal ratio reaches 100%, and therefore the residual tetragonal ratio in the sintered body of the present embodiment is 100% or less, and further 95% or less.

The greater the content of the additive component, the more the hydrothermal degradation tends to be suppressed. In the sintered body of the present embodiment, when the content of the additive component is 0 mass%, that is, when the additive component is not contained, the residual tetragonal crystal ratio may be 15% or more and 100% or less, preferably 20% or more and 100% or less, and more preferably 50% or more and 80% or less. In the case where the sintered body of the present embodiment contains an additive component and the content of the additive component is more than 0 mass% and less than 5 mass%, the residual tetragonal crystal ratio may be, for example, 65% or more and 100% or less, and preferably 70% or more and 90% or less. In the case where the sintered body of the present embodiment contains an additive component and the content of the additive component is 5% by mass or more and 30% by mass or less, the residual tetragonal crystal ratio may be 70% or more and 100% or less, and preferably 76% or more and 95% or less, for example.

The shape of the sintered body of the present embodiment may be any desired shape, and may be any basic shape such as a cubic shape, a rectangular parallelepiped shape, a polyhedral shape, a plate shape, a disc shape, a columnar shape, a conical shape, a spherical shape, or a substantially spherical shape, as long as it is a shape of a member according to various uses.

The method for producing the sintered body of the present embodiment is arbitrary, and is preferably produced by a production method using, as a raw material, a powder containing zirconia containing a stabilizer and having a monoclinic ratio of more than 70% and characterized in that the monoclinic zirconia has a crystal grain diameter of more than 23nm and 80nm or less. Such powder may be molded and then sintered by a known method. If necessary, at least one of the pre-firing and the processing may be performed before the sintering.

The molding may be carried out by a known method, for example, at least 1 selected from uniaxial pressing, cold isostatic pressing, slip casting and injection molding, and preferably at least 1 selected from uniaxial pressing, cold isostatic pressing and injection molding.

The calcination may be carried out by heat-treating the powder at a temperature lower than the sintering temperature, for example, at a temperature of 800 ℃ or higher and lower than 1200 ℃ in the air.

The sintering may be carried out by a known method, for example, by 1 or more selected from the group consisting of pressure sintering, vacuum sintering and atmospheric sintering. In view of simplicity and ease of industrial application, the sintering is preferably atmospheric sintering, more preferably atmospheric sintering in the air at 1200 ℃ to 1550 ℃ inclusive, preferably 1250 ℃ to 1500 ℃ inclusive, and further preferably atmospheric sintering in the air at 1300 ℃ to 1450 ℃ inclusive. Further, it is preferable that sintering other than atmospheric sintering is not performed.

The sintered body of the present embodiment can be used as a member including the sintered body for a known use of a zirconia sintered body. The sintered body of the present embodiment is suitable as a structural material for a pulverizer member, a precision machine member, an optical connector member, and the like; biological materials such as dental materials; and exterior materials such as decorative members and electronic equipment exterior parts.

The powder of the present embodiment will be described below.

The present embodiment is a powder comprising zirconia containing a stabilizer and having a monoclinic rate of more than 70%, wherein the monoclinic zirconia has a crystal grain diameter of more than 23nm and 80nm or less.

The powder of the present embodiment contains zirconia containing a stabilizer and having a monoclinic ratio of more than 70%. That is, the powder of the present embodiment contains a stabilizer-containing zirconia mainly composed of monoclinic zirconia. In the case of a powder containing zirconia without a stabilizer, it is difficult to obtain a sintered body containing tetragonal zirconia, which is a cause of showing fracture toughness, even when the powder is sintered. The powder of the present embodiment is a so-called zirconia powder mainly composed of zirconia.

Examples of the stabilizer include calcium oxide (CaO), magnesium oxide (MgO), and cerium oxide (CeO)₂) And yttrium oxide (Y)₂O₃) Preferably at least one of cerium oxide and yttrium oxide, and more preferably yttrium oxide. When the stabilizing agent is yttria, the yttria in the powder is relative to zirconia (ZrO)₂) And yttrium oxide (Y)₂O₃) The total molar ratio (yttrium oxide content) of (a) is, for example, 1.0 mol% or more and 2.5 mol% or less, further 1.1 mol% or more and 2.0 mol% or less, preferably 1.2 mol% or more and less than 2.0 mol%, more preferably 1.2 mol% or more and 1.8 mol% or less.

The stabilizer is preferably solid-dissolved in the zirconia, and the powder of the present embodiment preferably does not contain an undissolved stabilizer.

Monoclinic zirconia, tetragonal zirconia, and cubic zirconia are known as main crystal phases of zirconia. The zirconia in the powder of the present embodiment includes monoclinic zirconia, preferably includes monoclinic zirconia, and at least one selected from tetragonal zirconia and cubic zirconia, and more preferably includes monoclinic zirconia and tetragonal zirconia.

The monoclinic ratio of zirconia is more than 70%, preferably 80% or more, and more preferably 85% or more. When the monoclinic ratio is 100% or less and the zirconia contains at least either tetragonal zirconia or cubic zirconia, the monoclinic ratio is less than 100%. The tetragonal crystal ratio is 30% or less, further less than 20%, preferably 15% or less, and may be 10% or less, further 7% or less. When the zirconia does not contain tetragonal zirconia, the tetragonal crystal ratio may be 0%, or the tetragonal crystal ratio may be 0% or more.

Grain size (D) of monoclinic zirconia_m) Is more than 23nm and 80nm or less, more preferably 30nm or more and 60nm or less, and still more preferably 35nm or more and 55nm or less. In another embodiment, the monoclinic zirconia has a crystal grain diameter (D)_m) Examples thereof include 30nm to 50nm, more preferably 35nm to 50nm, still more preferably 35nm to 45nm, still more preferably 36nm to 40 nm.

The powder of the present embodiment may comprise a material selected from alumina (Al)₂O₃) Germanium oxide (GeO)₂) And silicon dioxide (SiO)₂) 1 or more of the above-mentioned additives. The additive component is preferably at least one of alumina and germanium oxide, and more preferably alumina. By including the additive component, even when the content of the stabilizer of zirconia is small, defects such as cracks are less likely to occur during sintering, and the yield during sintering is less likely to decrease. The content of the additive component is 0.05 mass% or more and 30 mass% or less, preferably more than 0.1 mass% and 25 mass% or less, more preferably 0.2 mass% or more and 20 mass% or less, and further preferably 0.23 mass% or more and 6 mass% or less, as the mass ratio of the additive component to the total mass of the zirconia, the yttria, and the additive component in the powder.

The powder of the present embodiment preferably does not contain impurities, and for example, the content of phosphorus (P) may be 0.1 mass% or less and less than 0.1 mass%, respectively. On the other hand, hafnium oxide (HfO) among zirconium oxides may be contained₂) And the like.

The BET specific surface area of the powder of the present embodiment can be, for example, 6m²More than or equal to g and less than 20m²(ii) in terms of/g. By making the BET specific surface area 6m²More than g, the sintering is easy to start from a lower temperature. In addition, below 20m²In the case of/g, physical aggregation of the powder tends to be suppressed. In order to more easily obtain these effects, the BET specific surface area is preferably 8m²More than or equal to 18m²A ratio of 10m or less per gram²More than g and 17m²A ratio of 10m or less per gram²More than 15 m/g²A value of less than or equal to g, more preferably greater than 10m²A number of grams per gram of the composition is 15m²The ratio of the carbon atoms to the carbon atoms is less than g.

The median particle diameter of the powder of the present embodiment is preferably 0.05 μm or more and 0.3 μm or less, and preferably 0.1 μm or more and 0.2 μm or less.

The volume particle size distribution curve of the powder of the present embodiment may exemplify a multimodal distribution, and the volume particle size distribution curve is preferably a distribution having peaks at least at a particle size of 0.05 μm or more and 0.2 μm or less and a particle size of more than 0.2 μm and 0.5 μm or less, and further a distribution having peaks (extrema) at a particle size of 0.05 μm or more and 0.2 μm or less and a particle size of 0.3 μm or more and 0.5 μm or less. A powder having a multimodal volume particle size distribution curve such as a bimodal distribution tends to have an improved filling property during molding. When the ratio of the peak having a particle diameter of 0.3 μm or more and 0.5 μm to the peak having a particle diameter of 0.05 μm or more and 0.2 μm or less (hereinafter also referred to as "particle diameter peak ratio") in the volume particle diameter distribution curve is more than 0 and less than 1, further more 0.1 or more and 0.9 or less, and still more 0.2 or more and 0.8 or less, the density of the resulting molded article tends to be high, which is preferable.

The powder of the present embodiment preferably has high moldability, and when the powder of the present embodiment is uniaxially pressed under a pressure of 70 ± 5MPa and then subjected to cold isostatic pressing (hereinafter also referred to as "CIP") treatment under a pressure of 196 ± 5MPa to prepare a molded body, the relative density of the molded body (hereinafter also referred to as "molded body density") is preferably 49% or more and 56% or less, and more preferably 50% or more and 54% or less.

The powder of the present embodiment may contain a resin or the like for improving fluidity, or may be prepared as a composition (hereinafter also referred to as "composite") containing the powder of the present embodiment and the resin. The resin contained in the composite may be any known resin used in ceramic compositions, and examples thereof include thermoplastic resins. Preferable resins include 1 or more selected from acrylic resins, polystyrene, and polyalkyl carbonate, and acrylic resins are preferable.

The content of the powder in the composite may be 50 mass% or more and 97 mass% or less, 70 mass% or more and 95 mass% or less, 80 mass% or more and 90 mass% or less, or the like, as a mass ratio of the powder with respect to the mass of the composite. The content of the powder in the composite may be determined from the mass ratio of the composite from which the resin has been removed to the mass of the composite. The method of removing the resin is arbitrary, and examples thereof include heat treatment at 200 ℃ to 500 ℃ in the atmosphere.

The composite may contain a component such as wax as an additive in addition to the resin. By including these components, additional effects such as favorable releasability from the molding die can be obtained. Examples of the component such as wax include 1 or more selected from polyethylene, polypropylene, polyacrylonitrile, acrylonitrile-styrene copolymer, ethylene-vinyl acetate copolymer, styrene-butadiene copolymer, polyacetal resin, petroleum wax, synthetic wax, vegetable wax, stearic acid, phthalate plasticizer, and adipate.

The powder of the present embodiment can be used as a precursor of a calcined body or a sintered body, and is suitable as a structural material for a member for a pulverizer, a precision machine component, an optical connector component, or the like; biological materials such as dental materials; raw material powder for exterior materials such as exterior members of electronic devices and the like.

When the powder of the present embodiment is formed into a sintered body or the like, the powder may be molded and then calcined or sintered by a known method.

When the powder of the present embodiment is formed into a molded article, the molding may be performed by a known method, for example, at least 1 selected from uniaxial pressing, cold isostatic pressing, slip casting, and injection molding. When a composite or the like is molded using a resin, the resin may be removed by heat treatment of the obtained molded article, if necessary. The heat treatment conditions may be, for example, 400 ℃ or higher and less than 800 ℃ in the atmosphere.

The molded article may be subjected to calcination as necessary. The pre-firing may be performed by heat treatment at a temperature lower than the sintering temperature of the powder, for example, at a temperature of 800 ℃ or higher and lower than 1200 ℃ in the air. Thus, a calcined body was obtained.

The sintering may be carried out by a known method, for example, by 1 or more selected from the group consisting of pressure sintering, vacuum sintering and atmospheric sintering. For simplicity and ease of industrial application, the sintering is preferably atmospheric sintering, which is performed in the air at 1200 ℃ to 1550 ℃, preferably 1250 ℃ to 1500 ℃, and more preferably atmospheric sintering in the air at 1300 ℃ to 1450 ℃. Further, it is preferable not to perform sintering other than atmospheric sintering. The sintering time is arbitrary, and may be, for example, 0.5 hours or more and 5 hours or less.

Next, a method for producing the powder of the present embodiment will be described.

The powder of the present embodiment may be produced by any method as long as it has the above-described characteristics. A preferred method for producing the powder of the present embodiment includes the steps of: a step of heat-treating a composition containing a zirconia sol and a stabilizer source at a temperature of 950 ℃ to 1250 ℃ to prepare a calcined powder; and a step of pulverizing the calcined powder, wherein the zirconia sol has an average sol particle diameter of 150nm to 400nm and contains zirconia containing monoclinic zirconia.

A step of heat-treating a composition containing a zirconia sol having an average sol particle diameter of 150nm or more and 400nm or less and containing zirconia containing monoclinic zirconia and a stabilizer source at a temperature of 950 ℃ or more and 1250 ℃ or less to prepare a calcined powder (hereinafter, also referred to as "powder calcining step"), thereby obtaining a calcined powder as a precursor of the powder of the present embodiment.

In the powder pre-firing step, heat treatment is performed at a temperature of 950 ℃ to 1250 ℃, and further at a temperature of 1000 ℃ to 1250 ℃. By setting the heat treatment temperature to 950 ℃ or higher, a powder which is easily densified by atmospheric pressure sintering can be obtained. On the other hand, by setting the heat treatment at 1250 ℃ or less, a powder which is easily dispersed by pulverization can be easily obtained. The time of the heat treatment varies depending on the heat treatment temperature, and examples thereof include 30 minutes to 2 hours.

The atmosphere for the heat treatment is arbitrary, and any one selected from an oxidizing atmosphere, a reducing atmosphere, an inert atmosphere, and a vacuum atmosphere can be exemplified, but an oxidizing atmosphere is preferable, and an atmospheric atmosphere is more preferable.

The zirconia sol has an average sol particle diameter of 150nm to 400nm, preferably 180nm to 400nm, and more preferably 185nm to 300 nm. The average sol particle diameter may be 150nm to 270nm, further 150nm to 200nm, or 190nm to 400nm, further 200nm to 300 nm.

The zirconia sol contains zirconia containing monoclinic zirconia, preferably a zirconia sol containing zirconia containing crystalline zirconia (hereinafter also referred to as "crystalline zirconia sol"), more preferably a zirconia sol containing crystalline zirconia whose main phase is monoclinic zirconia.

The amount of zirconium element (hereinafter also referred to as "adsorbed zirconium amount") of the zirconia sol determined by the following formula is preferably 0 mass% or more and 1 mass% or less, more preferably 0 mass% or more and 0.5 mass% or less, and still more preferably 0 mass% or more and 0.01 mass% or less, because it tends to be easily pulverized.

W_Zr＝(m/m₀)×100

In the above formula, W_ZrThe amount of adsorbed zirconium (mass%) was determined. m is a slurry obtained by dispersing a zirconia sol in pure water, subjecting the slurry to ultrafiltration using an ultrafiltration membrane having a molecular weight cut-off of 500 to 300 ten thousand, and converting the amount of zirconium in the obtained filtrate into oxygenZirconium (ZrO) oxide₂) Mass (mg) in time. The amount of zirconium in the filtrate was determined by ICP analysis. m is₀The mass (mg) of the zirconia sol before ultrafiltration was measured after heat treatment at 1000 ℃ for 1 hour in an atmospheric atmosphere. m and m₀The measurement of (2) can be performed by preparing the same amount of the zirconia sol before ultrafiltration.

The zirconia sol to be subjected to the powder calcination step may have the above-described characteristics, and the production method thereof is arbitrary. As a method for producing the zirconia sol, at least either one of a hydrothermal synthesis method and a hydrolysis method can be exemplified. In the hydrothermal synthesis method, a zirconium salt, an alkali, and the like are mixed in the presence of a solvent to obtain a coprecipitate, and the coprecipitate is heat-treated at 100 to 200 ℃ to obtain a zirconia sol. In the hydrolysis method, a zirconium salt is heated in the presence of a solvent, and the zirconium salt is hydrolyzed to obtain a zirconia sol. As described above, the zirconia sol can be exemplified by a zirconia sol obtained by a hydrothermal synthesis method or a hydrolysis method, and preferably a zirconia sol obtained by a hydrolysis method.

Examples of the precursor used in the method for producing a zirconia sol include a zirconium salt. The zirconium salt may be exemplified by 1 or more selected from zirconium oxychloride, zirconium nitrate, zirconium chloride, and zirconium sulfate, preferably at least one of zirconium nitrate and zirconium oxychloride, and more preferably zirconium oxychloride.

Hereinafter, a preferred method for producing a zirconia sol will be described by way of example of a hydrolysis method.

The hydrolysis conditions may be any conditions that allow sufficient hydrolysis of the zirconium salt, and examples thereof include boiling and refluxing the aqueous solution of the zirconium salt for 130 hours to 200 hours. When the anion concentration in the aqueous solution of a zirconium salt is hydrolyzed to 0.2mol/L to 0.6mol/L, and further 0.3mol/L to 0.6mol/L, the average sol particle diameter tends to increase.

The stabilizer source may be at least one of a stabilizer and a compound as a precursor thereof, and may be, for example, an oxide, hydroxide, oxyhydroxide, chloride or the like as a precursor of a stabilizerThe salt is preferably at least one of chloride and nitrate. The stabilizer source is preferably at least any one of yttrium oxide and an yttrium compound as a precursor thereof. As a preferable stabilizer source (hereinafter, stabilizers containing yttrium oxide and the like are also referred to as "yttrium oxide source" and the like), 1 or more kinds selected from yttrium chloride, yttrium nitrate and yttrium oxide, and further at least one of yttrium chloride and yttrium oxide can be cited. In the case where the stabilizer source is an yttrium oxide source, the content of the yttrium oxide source in the composition is converted to Y as the yttrium oxide source in the composition₂O₃Then converted into ZrO based on zirconium (Zr) and yttrium (Y), respectively₂And Y₂O₃The molar ratio of the latter value in total can be, for example, 1.0 mol% or more and 2.5 mol% or less, further 1.1 mol% or more and 2.0 mol% or less, preferably 1.2 mol% or more and less than 2.0 mol%, and more preferably 1.2 mol% or more and 1.8 mol% or less.

The composition to be used in the powder calcination step may contain the zirconia sol and the stabilizer source, and all or a part of the stabilizer source may be dissolved in the zirconia sol.

For example, at least a part of the stabilizer source is easily dissolved in the zirconia by a method of mixing a zirconium salt and the stabilizer source to hydrolyze the zirconium salt, or mixing a zirconium salt, the stabilizer source, an alkali, and the like to prepare a coprecipitate.

The composition to be subjected to the powder calcination step may contain 1 or more additional component sources selected from an alumina source, a germanium oxide source and a silica source. The additive component source is preferably at least one of an alumina source and a germanium oxide source, and is preferably an alumina source.

The alumina source is at least one of alumina and an aluminum compound which is a precursor thereof, and may include 1 or more selected from the group consisting of alumina, aluminum hydroxide, aluminum nitrate and aluminum chloride, preferably alumina, and more preferably at least one of alumina sol and alumina powder.

The germanium oxide source is at least one of germanium oxide and a germanium compound which is a precursor thereof, and may be at least one selected from the group consisting of germanium oxide, germanium hydroxide and germanium chloride, preferably germanium oxide, and more preferably at least one of a germanium oxide sol and germanium oxide powder.

The silica source is at least one of silica and a silicon compound which is a precursor thereof, and may be 1 or more selected from silica and tetraethyl orthosilicate, and is preferably silica, and more preferably at least one of silica powder, silica sol, fumed silica, and precipitated silica.

The contents of the additive component sources are calculated by converting Al, Ge and Si in the composition into Al₂O₃、GeO₂And SiO₂The total of the mass of (A) is calculated by converting Zr, Y, Al, Ge and Si into ZrO₂、Y₂O₃And Al₂O₃、GeO₂And SiO₂The proportion of (b) is 0.05 to 30 mass%, preferably more than 0.1 to 25 mass%, and more preferably 0.2 to 20 mass%.

For example, the content of the alumina source is calculated as Al in terms of the alumina source in the composition₂O₃Relative to the conversion of Zr, Y and Al into ZrO respectively₂、Y₂O₃And Al₂O₃The proportion of (b) is 0.05 to 30 mass%, preferably more than 0.1 to 25 mass%, more preferably 0.2 to 20 mass%.

In addition, the content of the germanium oxide source is calculated as GeO in terms of the germanium oxide source in the composition₂Relative to the conversion of Zr, Y and Ge into ZrO respectively₂、Y₂O₃And GeO₂The proportion of (b) is 0.05 to 30 mass%, preferably more than 0.1 to 25 mass%, more preferably 0.2 to 20 mass%.

Further, regarding the content of the silica source, the content of the silica source is defined as the amount of the silica in the compositionConversion of chemical silicon source to SiO₂Relative to the conversion of Zr, Y and Si into ZrO respectively₂、Y₂O₃And SiO₂The proportion of (b) is 0.05 to 30 mass%, preferably more than 0.1 to 25 mass%, more preferably 0.2 to 20 mass%.

As the physical properties of the calcined powder, the BET specific surface area of 3m²More than 15 m/g²A monoclinic crystal grain diameter of 20nm to 60 nm.

In the step of pulverizing the calcined powder (hereinafter also referred to as "pulverizing step"), the calcined powder is subjected to a pulverizing treatment. Zirconia having a low stabilizer content is likely to cause cracks, defects, and the like during sintering. In contrast, by pulverizing the calcined powder in the present embodiment, the yield at the time of sintering is easily improved, and the obtained sintered body tends to be less susceptible to hydrothermal degradation.

In order to obtain a powder of a desired composition, a mixed powder of the calcined powder, the alumina source, and the additive component source may be pulverized in the pulverization step instead of the calcined powder. The additive component source may be exemplified by the additive component sources described above. In the case where the additive component sources are mixed in the pulverization step, the content of the additive component sources is calculated as Al in the mixed powder₂O₃Conversion of Ge into GeO₂Conversion of mass and Si into SiO₂The mass of (b) is calculated by converting Zr, Y and 1 or more selected from Al, Ge and Si in the mixed powder into ZrO₂、Y₂O₃And Al₂O₃、GeO₂And SiO₂The additive component source and the calcined powder may be mixed so that the total of the total mass ratio of (a) to (b) is 0.05 to 30 mass%, preferably more than 0.1 to 25 mass%, more preferably 0.2 to 20 mass%.

The grinding method is arbitrary, and at least either one of wet grinding and dry grinding is sufficient, and wet grinding is preferable. Specific examples of the wet grinding include 1 or more selected from ball milling, vibration milling and continuous medium stirring milling, and ball milling is preferable. The conditions for ball milling include, for example: the method comprises mixing a calcined powder with a solvent to prepare a slurry having a mass ratio of the calcined powder to the mass of the slurry of 30-60 mass%, and pulverizing the slurry for 10-100 hours using zirconia balls having a diameter of 1-15 mm as a pulverization medium.

After wet grinding, the powder may be prepared by drying the powder by any method. The drying conditions may be, for example, 110 to 130 ℃ in the air.

In order to improve the handling properties of the powder, the method for producing a powder according to the present embodiment may include a step of granulating the powder (hereinafter also referred to as "granulating step"). The granulation may be carried out by any method, and examples thereof include a method of spray granulation of a slurry obtained by mixing a powder and a solvent. The solvent is at least one of water and alcohol, and is preferably water. Examples of the granulated powder (hereinafter also referred to as "powder particles") include: an average particle diameter of 30 to 80 μm, and further 50 to 60 μm; and a bulk density of 1.00g/cm³Above and 1.40g/cm³The concentration of the organic solvent is 1.10g/cm³Above and 1.30g/cm³The following.

Examples

The present disclosure will be described below with reference to examples. However, the present disclosure is not limited to these embodiments.

(average sol particle size)

The average sol particle size of the zirconia sol was measured using a dynamic light scattering particle size distribution measuring apparatus (apparatus name: UPA-UT 151; manufactured by MicrotracBEL). As pretreatment of the sample, a solution containing a hydrous zirconia sol was suspended in pure water and dispersed for 3 minutes using an ultrasonic homogenizer.

(monoclinic ratio, tetragonal ratio, D of powder)_tAnd D_m)

An XRD spectrum of the powder sample was obtained using a conventional X-ray diffraction apparatus (trade name: UltimAIIV; manufactured by RIGAKU Co., Ltd.). The conditions for XRD measurement are as follows.

Ray source: CuK alpha line (lambda is 0.15418nm)

Measurement mode: continuous scanning

Scanning speed: 4 °/min

Step length: 0.02 degree

Measurement range: 2 theta is 26-33 DEG

Using the obtained XRD spectrum and the calculation program "PRO-FIT", the monoclinic ratio, the tetragonal ratio and D were determined by the equations (1), (2), (4) and (5), respectively_tAnd D_m。

(BET specific surface area)

The BET specific surface area of the powder sample was measured by a method in accordance with JIS R1626-. Before the measurement, the powder sample was subjected to a degassing treatment at 250 ℃ for 30 minutes in the air, and then subjected to a pretreatment.

(measurement of particle size distribution)

The volume particle size distribution curve of the powder sample was measured by HRA mode of a Microtrac particle size distribution analyzer (trade name: MT3000II, manufactured by MicrotracBEL Co., Ltd.), and the median particle size was measured. Before the measurement, the powder sample was suspended in pure water, dispersed for 10 minutes using an ultrasonic homogenizer, and subjected to pretreatment.

(Density of molded article)

The mass of the molded sample was measured by a balance, and the volume was determined by measuring the dimensions with a caliper. From the obtained mass and volume, the measured density was determined. The theoretical density is obtained from equations (5) to (8), and the measured density (ρ) is calculated from the theoretical density (ρ)₀) The relative density (%) was obtained as the density of the molded article.

(monoclinic ratio and monoclinic strength ratio of sintered body)

The XRD measurement was performed on the sintered body sample under the same conditions as the XRD measurement conditions of the powder sample. The monoclinic ratio and the monoclinic intensity ratio were determined by the expressions (1) and (3) using the obtained XRD spectrum and the calculation program "PRO-FIT".

In the XRD measurement, the following sintered body samples were used: after cutting the surface with a flat grinding disk, automatic polishing with water-resistant paper (No. 800), automatic polishing with diamond slurry having an average particle size of 3 μm, and automatic polishing with colloidal silica of 0.03 μm were carried out in this order to carry out mirror polishing treatment, thereby obtaining a sintered body sample having a surface roughness (Ra) of 0.04 μm or less. For the automatic polishing, an automatic polishing apparatus (product name: MECATECH 334, PRESI) was used.

(sintered body Density)

The measured density of the sintered body sample was measured by the archimedes method. Before the measurement, the mass of the dried sintered body was measured, and then the sintered body was placed in water and boiled for 1 hour for pretreatment. The theoretical density is obtained from equations (5) to (8), and the measured density (ρ) is calculated from the theoretical density (ρ)₀) The relative density (%) was obtained as the sintered body density.

(average grain size)

The average grain size was determined by planimetry using SEM photographs of sintered body samples observed by a field emission type scanning electron microscope. That is, a circle having a known area is drawn in the SEM photograph, and the number of crystal grains (Nc) in the circle and the number of crystal grains (Ni) on the circumference of the circle are counted.

The average crystal grain size was determined by the following formula, after the total number of crystal grains (Nc + Ni) reached 250 ± 50.

Average crystal grain size of (Nc + (1/2) × Ni)/(a/M)²)

In the above formula, Nc is the number of crystal grains in a circle, Ni is the number of crystal grains on the circumference of a circle, a is the area of a circle, and M is the magnification (5000 times) observed by a scanning electron microscope. When the number of crystal grains (Nc + Ni) in one SEM photograph is less than 200, a plurality of SEM observation charts are used so that (Nc + Ni) is 250 ± 50.

Before the measurement, the sintered body sample was mirror-polished and then subjected to a thermal etching treatment to be subjected to a pretreatment. For mirror polishing, after the surface of the sintered body was cut with a flat grinding disk, the surface was polished with a mirror polishing apparatus using diamond abrasives having average particle diameters of 9 μm, 6 μm and 1 μm in this order.

(fracture toughness value)

The fracture toughness value of the sintered body sample was measured by a method according to the SEPB method defined in JIS R1607. The measurement was carried out using a pillar-shaped sintered body sample having a width of 4mm and a thickness of 3mm by using an inter-fulcrum distance of 30mm, and the average value of 10 measurements was defined as a fracture toughness value.

(bending Strength)

The bending strength of the sintered body sample was measured by a three-point bending test in accordance with JIS R1601. The measurement was carried out using a column-shaped sintered body sample having a width of 4mm and a thickness of 3mm by using an inter-fulcrum distance of 30mm, and the average value of 10 measurements was taken as the bending strength.

(all light transmittance)

The total light transmittance was measured by a method in accordance with JIS K7361 using a spectrophotometer (device name: V-650; manufactured by Japan Spectroscopy). For the measurement, a disc-shaped sample was used. Before the measurement, both surfaces of the sample were polished so that the sample had a thickness of 1mm and a surface roughness (Ra) of 0.02 μm or less. Light having a wavelength of 220 to 850nm was transmitted through the sample, and the transmittance at each wavelength was measured by condensing the light with an integrating sphere, and the transmittance at a wavelength of 600nm was defined as the total light transmittance.

Example 1

An aqueous zirconium oxychloride solution having a zirconium concentration and a chloride ion concentration of 0.4mol/L, respectively, was hydrolyzed. The hydrolyzed aqueous solution was subjected to ultrafiltration using an ultrafiltration membrane (cut-off molecular weight: 6000) to obtain a zirconia sol having an average sol particle size of 250 nm. W of the zirconia sol obtained_ZrIs not more than the detection limit (not more than 0.01 mass%).

Adding yttrium chloride hexahydrate and an ammonia water solution into the ultrafiltered zirconia sol water solution in a manner that yttrium oxide reaches 1.6 mol%, and obtaining a precipitate. The obtained precipitate was washed with pure water and dried in the air, and then presintered at a presintering temperature of 1025 ℃ in the air for 2 hours to obtain a presintered powder. The BET specific surface area of the obtained calcined powder was 12.5m²The monoclinic crystal grain size is 35 nm.

This calcined powder was mixed in pure water to prepare a slurry, which was then ball-milled using zirconia balls, and then dried at 120 ℃ in the atmosphere to obtain a powder containing yttria-containing zirconia having a yttria content of 1.6 mol%, which was used as the powder of this example. In the powder of this example, yttria was entirely dissolved in zirconia, and its crystal phases were monoclinic zirconia and tetragonal zirconia. Further, the median particle diameter was 0.15 μm, the volume particle diameter distribution curve was a bimodal distribution having peaks at a particle diameter of 0.14 μm and a particle diameter of 0.33 μm, and the particle diameter peak ratio was 0.39.

The powder of this example was subjected to die pressing at a pressure of 70MPa and CIP treatment at a pressure of 196MPa to prepare a molded article. The obtained molded body was sintered in the atmosphere at a sintering temperature of 1300 ℃ for 2 hours under normal pressure to obtain a sintered body.

Example 2

Mixing the pre-sintered powder with Al₂O₃Ball-milling the mixed powder of alumina sol in an amount of 0.25 mass% in terms of conversion; except for this, Al was contained in the alloy in the same manner as in example 1₂O₃Alumina in a reduced amount of 0.25 mass%, and the balance consisting of zirconia containing 1.6 mol% of yttria. The powder of this example had a median particle diameter of 0.15 μm, a volume particle diameter distribution curve of a bimodal distribution having peaks at a particle diameter of 0.14 μm and a particle diameter of 0.32 μm, and a particle diameter peak ratio of 0.37.

The powder was used with the sintering temperature set at 1250 ℃; except for this, a molded body and a sintered body were obtained in the same manner as in example 1.

Example 3

Setting the pre-sintering temperature at 1130 deg.c and mixing the pre-sintered powder with Al₂O₃Ball-milling the mixed powder of alumina sol in an amount of 0.25 mass%; except for this, Al was contained in the alloy in the same manner as in example 1₂O₃Alumina in a reduced amount of 0.25 mass%, and the balance consisting of zirconia containing 1.6 mol% of yttria.

The BET specific surface area of the obtained calcined powder was 6.7m²The monoclinic crystal grain size is 44 nm. Further, the median particle diameter of the powder of this example was 0.18. mu.mThe volume particle size distribution curve is a bimodal distribution having peaks at a particle size of 0.14 μm and a particle size of 0.36 μm, and the particle size peak ratio is 0.85.

Using the powder; except for this, a molded body and a sintered body were obtained in the same manner as in example 1.

Example 4

Adding yttrium chloride hexahydrate into the ultrafiltered zirconia sol water solution in a manner that yttrium oxide reaches 2 mol%, and mixing the pre-sintered powder with Al₂O₃Ball-milling the mixed powder of alumina sol in an amount of 0.25 mass% in terms of conversion; except for this, Al was contained in the alloy in the same manner as in example 1₂O₃Alumina in a reduced amount of 0.25 mass%, and the balance consisting of zirconia containing 2 mol% of yttria. The powder of this example had a median particle diameter of 0.15 μm, a volume particle diameter distribution curve of a bimodal distribution having peaks at a particle diameter of 0.14 μm and a particle diameter of 0.33. mu.m, and a particle diameter peak ratio of 0.33.

The powder was used with the sintering temperature set to 1500 ℃; except for this, a molded body and a sintered body were obtained in the same manner as in example 1.

Example 5

Mixing the pre-sintered powder with Al₂O₃Ball-milling 20 mass% of the mixed powder of alumina powder; except for this, Al was contained in the alloy in the same manner as in example 1₂O₃20 mass% of alumina and the balance consisting of zirconia containing 1.6 mol% of yttria. The powder of this example had a median particle diameter of 0.15 μm, a volume particle diameter distribution curve of a bimodal distribution having peaks at a particle diameter of 0.14 μm and a particle diameter of 0.35 μm, and a particle diameter peak ratio of 0.33. Further, the crystal grain diameter (D) of tetragonal zirconia_t) Was 42 nm.

Using the powder, and setting the sintering temperature to 1350 ℃; except for this, a molded body and a sintered body were obtained in the same manner as in example 1.

Example 6

Setting the pre-sintering temperature at 1130 deg.c and mixing the pre-sintered powder with Al₂O₃Conversion to 20 qualityBall milling the mixed powder of alumina powder in certain weight percentage; except for this, Al was contained in the alloy in the same manner as in example 1₂O₃20 mass% of alumina and the balance consisting of zirconia containing 1.6 mol% of yttria. The powder of this example had a median particle diameter of 0.16 μm, a volume particle diameter distribution curve of a bimodal distribution having peaks at a particle diameter of 0.14 μm and a particle diameter of 0.35 μm, and a particle diameter peak ratio of 0.67.

The powder was used with the sintering temperature set to 1400 ℃; except for this, a molded body and a sintered body were obtained in the same manner as in example 1.

Example 7

Adding yttrium chloride hexahydrate into the ultrafiltered zirconia sol water solution in a manner that yttrium oxide reaches 2 mol%, and mixing the pre-sintered powder with Al₂O₃Ball-milling 5 mass% of mixed powder of alumina sol; except for this, Al was contained in the alloy in the same manner as in example 1₂O₃5 mass% of alumina was converted, and the balance was made of zirconia containing 2 mol% of yttria. The powder of this example had a median particle diameter of 0.15 μm, a volume particle diameter distribution curve of a bimodal distribution having peaks at a particle diameter of 0.14 μm and a particle diameter of 0.35 μm, and a particle diameter peak ratio of 0.41.

The powder was used with the sintering temperature set to 1500 ℃; except for this, a molded body and a sintered body were obtained in the same manner as in example 1.

Example 8

Mixing the pre-sintered powder with Al₂O₃Ball-milling the mixed powder of 0.5 mass% of alumina sol; except for this, Al was contained in the alloy in the same manner as in example 1₂O₃0.5 mass% of alumina and the balance of zirconia containing 1.6 mol% of yttria. The median particle diameter of the powder of this example was 0.15 μm, and the volume particle diameter distribution curve was a bimodal distribution having peaks at a particle diameter of 0.14 μm and a particle diameter of 0.32 μm, and the particle diameter peak ratio was 0.49.

The powder was used with the sintering temperature set at 1250 ℃; except for this, a molded body and a sintered body were obtained in the same manner as in example 1.

Example 9

Mixing the pre-sintered powder with Al₂O₃Ball-milling 1 mass% of mixed powder of alumina sol; except for this, Al was contained in the alloy in the same manner as in example 1₂O₃1 mass% of alumina and the balance consisting of zirconia containing 1.6 mol% of yttria. The powder of this example had a median particle diameter of 0.15 μm, a volume particle diameter distribution curve of a bimodal distribution having peaks at a particle diameter of 0.14 μm and a particle diameter of 0.34 μm, and a particle diameter peak ratio of 0.49.

The powder was used with the sintering temperature set at 1250 ℃; except for this, a molded body and a sintered body were obtained in the same manner as in example 1.

Example 10

Mixing the pre-sintered powder with GeO₂Ball-milling the mixed powder of germanium oxide converted to 0.25 mass%; except for this, GeO was contained in the same manner as in example 1₂0.25% by mass in terms of germanium oxide, and the balance consisting of zirconium oxide containing 1.6 mol% of yttrium oxide. The powder of this example had a median particle diameter of 0.14 μm, a volume particle diameter distribution curve of a bimodal distribution having peaks at a particle diameter of 0.14 μm and a particle diameter of 0.34 μm, and a particle diameter peak ratio of 0.37.

The powder was used with the sintering temperature set at 1250 ℃; except for this, a molded body and a sintered body were obtained in the same manner as in example 1.

Example 11

Mixing the pre-sintered powder with SiO₂Ball-milling the mixed powder of silica sol in an amount of 0.25% by mass in terms of conversion; except for this, the same method as in example 1 was used to obtain a composition containing SiO₂0.25% by mass of silica in terms of the balance, and the balance being zirconia containing 1.6 mol% of yttria. The powder of this example had a median particle diameter of 0.18 μm, a volume particle diameter distribution curve of a bimodal distribution having peaks at a particle diameter of 0.14 μm and a particle diameter of 0.35 μm, and a particle diameter peak ratio of 0.89.

Using the powder, and setting the sintering temperature to 1350 ℃; except for this, a molded body and a sintered body were obtained in the same manner as in example 1.

Example 12

Mixing the pre-sintered powder with Al₂O₃0.25 mass% converted alumina sol and GeO₂Ball-milling the mixed powder of germanium oxide in an amount of 0.25 mass% in terms of the weight; except for this, Al was contained in the alloy in the same manner as in example 1₂O₃0.25 mass% of alumina and GeO₂0.25% by mass in terms of germanium oxide, and the balance consisting of zirconium oxide containing 1.6 mol% of yttrium oxide. The powder of this example had a median particle diameter of 0.15 μm, a volume particle diameter distribution curve of a bimodal distribution having peaks at a particle diameter of 0.14 μm and a particle diameter of 0.34 μm, and a particle diameter peak ratio of 0.37.

Using the powder, and setting the sintering temperature to 1200 ℃; except for this, a molded body and a sintered body were obtained in the same manner as in example 1.

Comparative example 1

An aqueous zirconium oxychloride solution having a zirconium concentration and a chloride ion concentration of 0.37mol/L and 0.74mol/L, respectively, was hydrolyzed. The hydrolyzed aqueous solution was ultrafiltered with an ultrafiltration membrane (cut-off molecular weight: 6000) to obtain a zirconia sol having an average sol particle size of 100 nm. W of the zirconia sol obtained_ZrThe content was 9% by mass.

Adding yttrium chloride hexahydrate and an ammonia water solution into the ultrafiltered zirconia sol water solution in a manner that yttrium oxide reaches 2 mol%, and obtaining a precipitate. The obtained precipitate was washed with pure water and dried in the atmosphere, and then presintered in the atmosphere at a presintering temperature of 1000 ℃ for 2 hours to prepare presintering powder.

This calcined powder was mixed in pure water to prepare a slurry, which was then ball-milled using zirconia balls, and then dried at 120 ℃ in the atmosphere to obtain a powder composed of yttria-containing zirconia having an yttria content of 2 mol%, which was used as the powder of this comparative example.

The powder of the comparative example was subjected to die pressing at a pressure of 70MPa and CIP treatment at a pressure of 196MPa to prepare a molded article. The obtained molded body was sintered in the atmosphere at a sintering temperature of 1450 ℃ for 2 hours under normal pressure to obtain a sintered body.

Comparative example 2

Mixing the pre-sintered powder with Al₂O₃Ball-milling a mixed powder of alumina powder in an amount of 0.25 mass% in terms of conversion; except for this, Al was contained in the alloy in the same manner as in comparative example 1₂O₃0.25% by mass of alumina in terms of powder, and the balance consisting of zirconia containing 2 mol% of yttria.

Using the powder; except for this, a molded body and a sintered body were obtained in the same manner as in comparative example 1.

Comparative example 3

Mixing the pre-sintered powder with Al₂O₃Ball-milling 5 mass% of the mixed powder of alumina powder; except for this, Al was contained in the alloy in the same manner as in comparative example 1₂O₃5 mass% of alumina was converted, and the balance was made of zirconia containing 2 mol% of yttria.

Using the powder; except for this, a molded body and a sintered body were obtained in the same manner as in comparative example 1.

Comparative example 4

Adding yttrium chloride hexahydrate and an ammonia water solution into the ultrafiltered zirconia sol water solution in a manner that yttrium oxide reaches 0.9 mol% to obtain a precipitate; except for this, by the same method as in example 1, a powder composed of zirconia containing 0.5 mol% of yttria was obtained.

The powder was subjected to die pressing at a pressure of 70MPa and CIP treatment at a pressure of 196MPa to prepare a molded article. The obtained molded article was sintered in the atmosphere at a sintering temperature of 1300 ℃ for 2 hours under normal pressure to obtain a sintered body, but the density was low and a large number of cracks were generated, and the characteristics of the sintered body could not be evaluated.

The evaluation results of the powders of the examples and comparative examples are shown in table 1, and the evaluation results of the sintered body are shown in table 2.

[ Table 1]

From the above table, it is understood that the contents of the stabilizer (yttrium oxide content) and the additive in the powders are the same in the examples and comparative examples 1 to 3, but D of comparative examples 1 to 3 is the same as that in the examples_mSmall, and low monoclinic rate. Further, it is understood that D in comparative example 4 is compared with the examples_mIs small.

[ Table 2]

From the above table, it is understood that the density of the molded article is 49% or more, further 50% or more in examples, and is less than 49% and further less than 48% in comparative examples, and the powder of the present examples has high filling property. On the other hand, it is understood that the sintered body density of the sintered body having the stabilizer content of 1.0 mol% or more is the same in both the examples and the comparative examples, but the fracture toughness value of the examples is 6.5MPa · m^0.5In contrast, the fracture toughness value of the comparative example was less than 6MPa · m^0.5A sintered body having high fracture toughness was obtained from the powder of this example by atmospheric pressure sintering. The sintered body of comparative example 1 had no XRD peak corresponding to the (111) plane of monoclinic zirconia, and therefore, the monoclinic intensity ratio could not be calculated. Further, the sintered body of comparative example 4 contains many defects such as cracks, and the sintered body is damaged when the measurement sample is processed by mirror polishing or the like, and therefore, measurement other than the density of the sintered body cannot be performed.

Further, with respect to the sintered bodies of examples 1 and 5, fracture toughness was measured by a method in accordance with the IF method specified in JIS R1607. The fracture toughness measured by the IF method was 17.9MPa m^1/5And 11.1MPa · m^1/5. The improvement in fracture toughness by the IF method and the SEPB method are different, but both of them have fracture toughness values higher than that by the SEPB method.

Example 13

By the same method as in example 1, a powder was obtained. Using the obtained powder and setting the sintering temperature to 1400 ℃; except for this, a sintered body was obtained in the same manner as in example 1.

Example 14

By the same method as in example 2, a powder was obtained. Using the obtained powder and setting the sintering temperature to 1350 ℃; except for this, a sintered body was obtained in the same manner as in example 2.

Example 15

By the same method as in example 3, a powder was obtained. Using the obtained powder and setting the sintering temperature to 1400 ℃; except for this, a sintered body was obtained in the same manner as in example 3.

Example 16

By the same method as in example 5, a powder was obtained. Using the obtained powder and setting the sintering temperature to 1500 ℃; except for this, a sintered body was obtained in the same manner as in example 5.

Example 17

By the same method as in example 6, a powder was obtained. Using the obtained powder and setting the sintering temperature to 1500 ℃; except for this, a sintered body was obtained in the same manner as in example 6.

Example 18

By the same method as in example 8, a powder was obtained. Using the obtained powder and setting the sintering temperature to 1350 ℃; except for this, a sintered body was obtained in the same manner as in example 8.

Example 19

By the same method as in example 9, a powder was obtained. Using the obtained powder and setting the sintering temperature to 1350 ℃; except for this, a sintered body was obtained in the same manner as in example 9.

Example 20

In the same manner as in example 10, a powder was obtained. Using the obtained powder and setting the sintering temperature to 1350 ℃; except for this, a sintered body was obtained in the same manner as in example 10.

Example 21

By the same method as in example 12, a powder was obtained. The powder obtained was used and the sintering temperature was set to 1250 ℃; except for this, a sintered body was obtained in the same manner as in example 12.

Example 22

By the same method as in example 12, a powder was obtained. Using the obtained powder and setting the sintering temperature to 1350 ℃; except for this, a sintered body was obtained in the same manner as in example 12.

Comparative example 5

In the same manner as in comparative example 1, a powder was obtained. Using the obtained powder and setting the sintering temperature to 1500 ℃; except for this, a sintered body was obtained in the same manner as in comparative example 1.

[ Table 3]

The sintered bodies of the examples had a fracture toughness value of 7MPa · m as measured by the SEPB method^0.5The above.

Measurement example 1 (hydrothermal degradation test)

A sintered body was obtained in the same manner as in example 2, mirror-polished, and then immersed in hot water at 140 ℃. In addition, as a comparative measurement example, a zirconia sintered body containing 3 mol% of yttria was treated and evaluated in the same manner. The results are shown in the following table.

The sintered body of the comparative measurement example was prepared by the following method: adding yttrium chloride hexahydrate into the ultrafiltered zirconia sol water solution in a manner that yttrium oxide reaches 3 mol%; except for this, the content of the compound (D) was 3 mol% in the same manner as in comparative example 1A powder of yttria and zirconia was subjected to CIP treatment under a mold pressure of 70MPa and a pressure of 196MPa to prepare a molded body, and the molded body was sintered in the atmosphere at a sintering temperature of 1500 ℃ for 2 hours under normal pressure. The sintered body of the comparative measurement example had a fracture toughness value of 4.8MPa · m^0.5。

[ Table 4]

In both the measurement examples and the comparative measurement examples of the sintered body before the hydrothermal degradation test, the main phase of the crystal phase was tetragonal zirconia. By the hydrothermal deterioration test, tetragonal zirconia was transformed into monoclinic zirconia, and thus the sintered body was deteriorated. As compared with the comparative measurement example, the measurement example was a sintered body having a low stabilizer content, but the monoclinic ratio after the hydrothermal degradation test was low, and the sintered body was not easily degraded. Since the sintered compact of the comparative measurement example before the hydrothermal degradation test had a monoclinic ratio of 0%, a tetragonal ratio of 70%, and the remainder was cubic, it was considered that the residual tetragonal ratio (Δ T%) was 4%; it is considered that almost all of the tetragonal zirconia of the sintered body was transformed into monoclinic zirconia by the hydrothermal degradation test for 10 hours. On the other hand, since the sintered body of the measurement example before the hydrothermal degradation test had a tetragonal crystal ratio of 94% and a monoclinic crystal ratio of 6%, it is considered that the residual tetragonal crystal ratio (Δ T%) was 85%, and further, even after the hydrothermal degradation test for 10 hours, a large amount of non-transformed tetragonal zirconia remained.

Measurement example 2 (residual tetragonal Crystal Rate)

The sintered bodies of examples 1 and 13 and comparative examples 1 and 5 were mirror-polished and then immersed in hot water at 140 ℃ for 6 hours to determine the residual tetragonal crystal ratio. The results are shown in the following table.

[ Table 5]

The residual tetragonal crystal ratio of the sintered body of the example was 65% or more, and it was found that the phase transition from tetragonal zirconia to monoclinic zirconia was less likely to occur as compared with the comparative example containing a large amount of the stabilizer.

Measurement example 3 (residual tetragonal Crystal Rate)

The sintered bodies of examples 2 to 4, 14 and 15 and comparative example 2 were mirror-polished and then immersed in hot water at 140 ℃ for 6 hours to determine the residual tetragonal crystal ratio. The results are shown in the following table.

[ Table 6]

The residual tetragonal crystal ratio of the sintered body of the example was 65% or more, and it was found that the phase transition from tetragonal zirconia to monoclinic zirconia was less likely to occur as compared with the comparative example. It is further understood that in example 4, the residual tetragonal crystal ratio was higher, although the sintering temperature was higher, as compared with comparative example 2.

Measurement example 4 (residual tetragonal Crystal Rate)

The sintered bodies of examples 5 to 12, 16 to 22 and comparative example 3 were mirror-polished and then immersed in hot water at 140 ℃ for 6 hours to determine the residual tetragonal crystal ratio. The results are shown in the following table.

[ Table 7]

The residual tetragonal crystal ratio of the sintered body of the example was 70% or more, and it was found that the phase transition from tetragonal zirconia to monoclinic zirconia was less likely to occur as compared with the comparative example. Further, the sintered body of example 22 was a sintered body containing alumina and germanium oxide as additive components in a total amount of 0.5 mass%. It can be seen that the sintered body of example 22 exhibited a residual tetragonal crystal ratio, although it was sintered at a higher temperature, compared to the sintered body of example 6 containing 20 mass% of alumina.

In addition, according to examples 1, 3 and 6 (and examples 5, 18 and 19) in which the sintering temperature and the content of the stabilizer were the same, the higher the content of the additive component (alumina), the higher the residual tetragonal crystal ratio tends to be.

Measurement example 5 (Total light transmittance)

The sintered bodies of examples 2, 8, 9 and 14 and comparative example 2 were used to measure the total light transmittance. The results are shown in the following table.

[ Table 8]

Although the additive components of the sintered bodies of the examples were all 0.2 mass% or more, the total light transmittance was 25% or more and 40% or less. Further, according to examples 2 and 14, as the sintering temperature increases, the total light transmittance becomes high. In contrast, the sintered body of comparative example 2 had a total light transmittance of less than 20%, although the sintering temperature was higher.

Further, the sintered body of example 2 was processed to have a thickness of 0.2mm, and the total light transmittance was measured in the same manner. As a result, the total light transmittance at a thickness of 0.2mm was 46%. When the sintered body of comparative example 2 was processed in the same manner, the sintered body was broken during the processing, and a measurement sample having a thickness of 0.2mm or less could not be obtained.

Measurement example 6 (Linear transmittance)

The sintered bodies of the examples were each processed to a specimen thickness of 0.09 mm. No cracks were generated, and the specimens were successfully processed into measurement specimens having a specimen thickness of 0.09 mm. The sintered compact of the comparative example was not processed to 0.2mm because defects such as cracks and fractures were generated during the processing.

The linear transmittance was measured for a sintered body having a specimen thickness of 0.09 mm. The values of the linear transmittance of the main examples are shown in the following table.

[ Table 9]

From examples 2, 3 and 14, it is understood that the linear transmittance decreases with an increase in the sintering temperature. Further, it is found that the sintered body of example 1 containing no alumina has a higher linear transmittance and the sintered body of example 8 has a lower linear transmittance than that of example 3. Further, from comparison among examples 11, 14, 20 and 21, it is understood that the linear transmittance differs depending on the type of the additive.

Measurement example 7 (evaluation of Compound)

Composites were made using the powders of examples 2 and 3, respectively. That is, after drying the powder at 150 ℃ for 1 hour or more, the powder and an acrylic resin were added to a kneader (model TDR-3, manufactured by TOSHIN Co., Ltd.) so that the mass of the powder was 85 mass% based on the mass of the resulting composite, and the mixture was kneaded at 160 ℃ to obtain a composite. 15 minutes after the start of kneading, the kneading properties of the compound were evaluated by measuring the torque (N · m) applied to the kneader. The smaller the value of the torque, the easier the compound can be kneaded, i.e., the more excellent the kneading property.

Fluidity was evaluated by measuring the flow rate of a compound sample with a flow tester. For the measurement, a syringe was filled with the composite by using a conventional flow tester (apparatus name: flow tester CFT 500D; manufactured by Shimadzu corporation). The compound was loaded under the following conditions, and the volume velocity (cm) of the compound ejected from the syringe was measured³S), from which fluidity was confirmed. The measurement conditions are shown below. The larger the value of the volume velocity, the more easily the compound flows in a molten state, i.e., the more excellent the fluidity.

Injector area: 1cm²

Die head aperture: diameter of 1mm

Die length: 2mm

Loading: 50kg of

Measuring temperature: 160 deg.C

Density of the composite: 3.0g/cm³

In addition, doFor comparative measurement, the BET specific surface area was similarly evaluated to be 15.0m²3 mol% yttria-containing zirconia powder having an average particle diameter (median particle diameter) of 1.1 μm/g. The evaluation results of the composite are shown in the following table. The powder of the comparative test example had low kneadability and could not be kneaded at 160 ℃. Accordingly, the kneading properties of the comparative test examples in the following table show values when kneaded at 170 ℃.

[ Table 10]

The powder of example 3 having a low BET specific surface area was excellent in both kneadability and flowability, and particularly, remarkably high in flowability, as compared with the powder of the comparative measurement example. Further, the powders of example 2 and comparative example have BET specific surface areas of the same degree as each other, but the flowability of the powder of example 2 is very high relative to the powder of comparative example. From these results, it is understood that the powders of the examples have excellent effects even when a composition (composite) comprising the powder and a resin is prepared.

The entire contents of the specification, claims and abstract of japanese patent application No. 2019-084550 filed on 25/4/31, japanese patent application No. 2019-142437 filed on 1/8/1 and japanese patent application No. 2019-211944 filed on 25/11/1 are incorporated herein as disclosures of the specification of the present disclosure.