阅读说明：本技术 氧化锆烧结体及其制造方法 (Zirconia sintered body and method for producing same ) 是由 伊藤武志 山内正一 山下勲 于 2020-03-24 设计创作，主要内容包括：本发明提供一种氧化锆烧结体及其制造方法中的至少任一者,所述氧化锆烧结体与包含透明氧化锆的现有的陶瓷接合体相比,能够应用于更广泛的用途。所述氧化锆烧结体具有透明氧化锆部和不透明氧化锆部,其特征在于,双轴弯曲强度为300MPa以上。(The present invention provides a zirconia sintered body which can be used in a wider range of applications than a conventional ceramic joined body including transparent zirconia, and at least one of a method for producing the same. The zirconia sintered body has a transparent zirconia part and an opaque zirconia part, and is characterized by having a biaxial bending strength of 300MPa or more.)

1. A zirconia sintered body characterized by having a transparent zirconia part and an opaque zirconia part and having a biaxial bending strength of 300MPa or more.

2. The zirconia sintered body according to claim 1, wherein the transparent zirconia portion and the opaque zirconia portion are on the same face.

3. The zirconia sintered body according to claim 1 or 2, wherein the transparent zirconia portion has a linear transmittance of 50% or more.

4. The zirconia sintered body according to any one of claims 1 to 3, wherein the opaque zirconia portion has a linear transmittance of less than 5%.

5. The zirconia sintered body according to any one of claims 1 to 4, wherein the transparent zirconia portion and the opaque zirconia portion contain zirconia containing a stabilizer and titania.

6. The zirconia sintered body according to claim 5, wherein the stabilizer is at least 1 selected from the group consisting of yttria, calcia and magnesia.

7. The zirconia sintered body according to claim 5 or 6, wherein the stabilizer of the transparent zirconia part is yttria, and a content of yttria is6 mol% or more and 12 mol% or less.

8. The zirconia sintered body according to any one of claims 5 to 7, wherein the stabilizer of the opaque zirconia portion is yttria, and a content of yttria is 2 mol% or more and less than 6 mol%.

9. The zirconia sintered body according to any one of claims 5 to 8, wherein the opaque zirconia part contains less titania than the transparent zirconia part.

10. The zirconia sintered body according to any one of claims 1 to 9, wherein the opaque zirconia portion contains a coloring element.

11. The zirconia sintered body according to claim 10, wherein the coloring element is at least 1 selected from the group consisting of a transition metal element, an alkali metal element, an alkaline earth metal element, aluminum, silicon, boron, phosphorus, germanium, and a rare earth element.

12. The zirconia sintered body according to any one of claims 1 to 11, wherein the biaxial bending strength is 350MPa or more.

13. The method for producing a zirconia sintered body according to any one of claims 1 to 12, comprising: and a sintering step of sintering a secondary molded body obtained by laminating a primary molded body of a raw material powder containing either a raw material powder of a transparent zirconia part or a raw material powder of an opaque zirconia part and a molded body of the other raw material powder.

14. The method for producing a zirconia sintered body according to claim 13, wherein each of the raw material powder of the transparent zirconia portion and the raw material powder of the opaque zirconia portion is a mixed powder containing a zirconia source containing a stabilizer and a titania source.

15. The method of manufacturing a zirconia sintered body according to claim 13 or 14, wherein sintering includes at least HIP treatment.

16. The manufacturing method according to any one of claims 13 to 15, wherein in the sintering, after the atmospheric pressure sintering is performed at 1300 ℃ or higher and 1400 ℃ or lower, the HIP treatment is performed at 1450 ℃ or higher and 1550 ℃ or lower.

Technical Field

The present disclosure relates to a zirconia sintered body and a method for producing the same.

Background

Ceramics are widely used for industrial members because of their excellent heat resistance, wear resistance, and corrosion resistance. Among them, transparent ceramics have been used in a wide range of applications because of their high aesthetic quality and texture. For example, applications of transparent ceramics to electronic device members such as cellular phones, timepiece members, jewelry, and the like have been studied. With such expansion of applications, it is expected to provide a ceramic member including a transparent ceramic and a ceramic having a color tone different from that of the transparent ceramic as a member having not only a higher aesthetic quality but also a higher design.

On the other hand, ceramics are materials with high toughness and are difficult to process into complicated shapes. Therefore, conventionally, a ceramic member having a complicated shape is manufactured by joining ceramics to each other.

For example, a ceramic joined body in which a colored zirconia sintered body is joined to a transparent zirconia sintered body by physically fixing the transparent zirconia sintered body by shrinking the colored zirconia sintered body has been reported (patent document 1).

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2013-14471

Disclosure of Invention

Technical problem to be solved by the invention

The ceramic joined body described in patent document 1 is a joined body produced by utilizing a difference in thermal shrinkage during heat treatment, and sintered bodies are joined to each other by physical force. The joined body has low strength and can be applied to a limited number of applications.

An object of the present disclosure is to provide a zirconia sintered body that can be applied to a wider range of uses than a conventional ceramic joined body including transparent zirconia, and at least one of a method for producing the zirconia sintered body.

Means for solving the problems

In view of the above-described technical problems, the present inventors have conducted studies. As a result, it has been found that the above-mentioned problems can be solved by a specific zirconia sintered body.

That is, the gist of the present disclosure is as follows.

[1] A zirconia sintered body having a transparent zirconia part and an opaque zirconia part, characterized by having a biaxial bending strength of 300MPa or more.

[2] The zirconia sintered body according to the above [1], wherein the transparent zirconia part and the opaque zirconia part are on the same surface.

[3] The zirconia sintered body according to the above [1] or [2], wherein the transparent zirconia portion has a linear transmittance of 50% or more.

[4] The zirconia sintered body according to any one of the above [1] to [3], wherein a linear transmittance of the opaque zirconia portion is less than 5%.

[5] The zirconia sintered body according to any one of the above [1] to [4], wherein the transparent zirconia part and the opaque zirconia part contain zirconia containing a stabilizer and titania.

[6] The zirconia sintered body according to the above [5], wherein the stabilizer is at least 1 selected from the group consisting of yttria, calcia and magnesia.

[7] The zirconia sintered body according to the above [5] or [6], wherein the stabilizer of the transparent zirconia part is yttria, and a content of yttria is6 mol% or more and 12 mol% or less.

[8] The zirconia sintered body according to any one of the above [5] to [7], wherein the stabilizer of the opaque zirconia portion is yttria, and a content of yttria is 2 mol% or more and less than 6 mol%.

[9] The zirconia sintered body according to any one of the above [5] to [8], wherein the opaque zirconia part has a smaller content of titanium oxide than the transparent zirconia part.

[10] The zirconia sintered body according to any one of the above [1] to [9], wherein the opaque zirconia portion contains a coloring element.

[11] The zirconia sintered body according to the above [10], wherein the coloring element is at least 1 selected from the group consisting of transition metal elements, alkali metal elements, alkaline earth metal elements, aluminum, silicon, boron, phosphorus, germanium, and rare earth elements.

[12] The zirconia sintered body according to any one of the above [1] to [11], characterized in that the biaxial bending strength is 350MPa or more.

[13] The method for producing a zirconia sintered body according to any one of [1] to [12], comprising: and a sintering step of sintering a secondary molded body obtained by laminating a primary molded body of a raw material powder containing either a raw material powder of a transparent zirconia part or a raw material powder of an opaque zirconia part and a molded body of the other raw material powder.

[14] The method of producing a zirconia sintered body according to the above [13], wherein the raw material powder of the transparent zirconia part and the raw material powder of the opaque zirconia part are mixed powders containing a zirconia source containing a stabilizer and a titania source, respectively.

[15] The method of producing a zirconia sintered body according to the above [13] or [14], wherein the sintering includes at least HIP treatment.

[16] The production method according to any one of [13] to [15], wherein, in the sintering, after the atmospheric pressure sintering at 1300 ℃ or higher and 1400 ℃ or lower, the HIP treatment is performed at 1450 ℃ or higher and 1550 ℃ or lower.

ADVANTAGEOUS EFFECTS OF INVENTION

The zirconia sintered body of the present disclosure can provide at least one of a zirconia sintered body and a method for producing the same, which can be applied to a wider range of uses than a conventional ceramic joined body including transparent zirconia.

Drawings

Fig. 1 is a schematic diagram showing measurement of biaxial bending strength.

Fig. 2 is a schematic view showing a cross section of the secondary molded body.

Fig. 3 is a schematic view showing the appearance (front surface and cross section) of the zirconia sintered body of example 1.

Detailed Description

The following description will explain an example of an embodiment of the zirconia sintered body of the present disclosure.

The present embodiment is a zirconia sintered body having a transparent zirconia part and an opaque zirconia part, characterized in that the biaxial bending strength is 300MPa or more.

The zirconia sintered body of the present embodiment has a transparent zirconia portion and an opaque zirconia portion. This easily improves the aesthetic quality and the design. In another embodiment, the zirconia sintered body of the present embodiment is a multicolor zirconia sintered body, that is, a zirconia sintered body having zirconia sintered bodies of 2 or more different color tones. In a further embodiment, the zirconia sintered body of the present embodiment is a sintered body having a light-transmitting zirconia sintered body and a light-opaque zirconia sintered body, and further, is a zirconia sintered body including a transparent zirconia sintered body which can be visually recognized and an opaque zirconia sintered body which can be visually recognized.

Still another embodiment is a zirconia sintered body containing zirconia having a cubic fluorite-type structure, and a zirconia sintered body containing zirconia having a tetragonal fluorite-type structure.

The zirconia sintered body of the present embodiment preferably has a structure obtained by sintering a transparent zirconia portion and an opaque zirconia portion, and more preferably has a structure obtained by sintering a transparent zirconia portion and an opaque zirconia portion in a state where an interface is formed. It is further preferred that the interface has no gaps. The phrase "having no gap" means that the interface between the transparent zirconia portion and the opaque zirconia portion is formed to a degree that the strength of the zirconia sintered body of the present embodiment is exhibited, and the zirconia sintered body of the present embodiment may have fine defects to a degree that the strength thereof is not affected. By having a structure in which the transparent zirconia part and the opaque zirconia are joined without using a third component such as a binder, the zirconia sintered body of the present embodiment is formed as a sintered body formed of an integral sintered structure, and the occurrence of breakage is reduced. Further, by having a structure in which the transparent zirconia portion and the opaque zirconia portion are sintered in a state where an interface is formed, the mechanical strength is likely to be further increased. Further, the zirconia sintered body of the present embodiment has a grain structure in which the crystal grains of the transparent zirconia portion and the crystal grains of the opaque zirconia portion are sintered, by having a structure in which the transparent zirconia portion and the opaque zirconia portion are joined without using the third component. Therefore, it is different from a zirconia sintered body not having such a grain structure, and a zirconia joined body obtained by simply fitting 2 or more kinds of zirconia sintered bodies. That is, the zirconia sintered body of the present embodiment is a joined body in a state in which the transparent zirconia portion and the opaque zirconia portion are joined by sintering, and is different from a joined body in a state in which the transparent zirconia portion and the opaque zirconia portion are joined only by a physical force.

In general, a transparent zirconia sintered body is lower in strength than an opaque zirconia sintered body. In contrast, the zirconia sintered body of the present embodiment has a structure in which the transparent zirconia portion and the opaque zirconia portion are sintered, and the strength of the transparent zirconia portion itself tends to be higher than that of the transparent zirconia sintered body alone.

The shape of the zirconia sintered body of the present embodiment is not particularly limited, and at least the transparent zirconia part and the opaque zirconia part are preferably on the same plane. In the present embodiment, "on the same plane" means on the same plane or on the same curved surface, and more preferably, the transparent zirconia portion and the opaque zirconia portion are on the same plane in a visually recognizable plane. The transparent zirconia portion and the opaque zirconia portion are arranged on the same surface, and thus the design is easily improved.

The zirconia sintered body of the present embodiment may have any shape, and may be, for example, spherical, approximately spherical, disc-shaped, cylindrical, elliptic cylindrical, plate-shaped, cubic, rectangular parallelepiped, polyhedral, approximately polyhedral, or a shape suitable for other applications. Further, for example, a shape including a structure in which either one of the transparent zirconia portion and the opaque zirconia portion is disposed so as to surround the other, such as a shape shown in fig. 1 of patent document 1, may be adopted, and a shape having a structure in which the opaque zirconia portion surrounds the transparent zirconia portion is preferable.

The zirconia sintered body of the present embodiment may be obtained by sintering a molded body or the like in which the precursor of the transparent zirconia portion and the precursor of the opaque zirconia portion are in contact with each other without a gap. Therefore, the zirconia sintered body of the present embodiment has a high degree of freedom in shape, and can be obtained as a zirconia sintered body having a complicated shape. For example, the zirconia sintered body of the present embodiment may include the following structure: either the transparent zirconia portion or the opaque zirconia portion has an uneven shape, and the other is laminated so as to combine the uneven shape.

The ratio of the transparent zirconia portion to the opaque zirconia portion in the zirconia sintered body of the present embodiment can be arbitrarily selected depending on the desired aesthetic quality and shape, and for example, as a volume ratio, a transparent zirconia portion and an opaque zirconia portion are 1:99 to 99: 1.

The zirconia sintered body of the present embodiment may have a structure in which one of the transparent zirconia portion and the opaque zirconia portion is patterned on the surface of the other. Here, the "pattern" refers to a line pattern, a pattern, or a combination thereof formed on one of the transparent zirconia portion and the opaque zirconia portion in the visually recognizable portion of the zirconia sintered body of the present embodiment, such as the surface, and composed of the other zirconia portion. The line diagrams include solid lines, broken lines, wavy lines, and other linear shapes, numerals, characters, symbols, and the like; as the figure, a polygon such as a triangle, a quadrangle, or a pentagon, a geometric shape such as a circle or an ellipse, or the like can be illustrated. Examples of the pattern include a pattern formed in a thickness of 1cm²Area below, further 1mm²The following region, still further 0.5mm²The following region, still further 0.05mm²The following region, still further 0.005mm²The following region. Further, canThere are illustrated line graphs including lines having a thickness of about 150 μm, line graphs and patterns spaced apart by about 150 μm, and patterns having a diameter of 1mm or less, and further having a diameter of 0.5mm or less.

From the viewpoint of having particularly excellent aesthetic properties, the zirconia sintered body of the present embodiment is preferably free from the bleeding phenomenon. The bleeding phenomenon can be considered to be caused by the coloring element of one of the transparent zirconia portion or the opaque zirconia portion diffusing to the other zirconia portion by a certain amount or more. Here, the "coloring element" refers to an element that imparts a coloring effect to zirconia, and is an ion, an oxide, a composite oxide, or the like, and the state of existence thereof is not limited. In the present embodiment, the "bleeding phenomenon" refers to a state in which a coloring element of one of the transparent zirconia portion and the opaque zirconia portion is contained in the other, and is observed mainly in the interface between the transparent zirconia portion and the opaque zirconia portion and in a region in the vicinity of the interface (hereinafter also referred to as "transition region"), visually or with an optical microscope.

From the viewpoint of forming a zirconia sintered body having more excellent aesthetic properties, the content of the coloring element in the region of the transparent zirconia portion within 20 μm from the interface is preferably 0.5 mass% or less, and more preferably 0.3 mass% or less. The content of the coloring element in the transfer region can be determined by compositional analysis using EPMA or the like.

The zirconia sintered body of the present embodiment is measured by the ratio of the volume measured by the archimedes method to the mass measured by measuring the mass (g/cm)³) The density (hereinafter also referred to as "measured density") was determined, and it is shown by way of example that the density is 5.8g/cm³Above and 6.10g/cm³The following, further 5.9g/cm³Above and 6.0g/cm³The following.

The relative density of the zirconia sintered body of the present embodiment is preferably 99.5% or more, more preferably 99.7% or more, and further preferably 99.9% or more.

In the present embodiment, the relative density of the zirconia sintered body can be obtained by the following formula.

Relative density (%). measured density (g/cm) of zirconia sintered body³) Apparent true density of zirconia sintered body (g/cm) (see かけ true density)³)×100

The actual measured density (sintered body density) of the zirconia sintered body is a density obtained by the archimedes method, and the apparent true density of the zirconia sintered body is a density calculated by the following formula based on the apparent true density and volume ratio of each of the transparent zirconia portion and the opaque zirconia portion.

M＝(Ma·X+Mb·Y)/(X+Y)

In the above formula, M is the apparent true density (g/cm) of the zirconia sintered body³) And Ma is the apparent true density (g/cm) of the transparent zirconia portion³) Mb is the apparent true density (g/cm) of the opaque zirconia portion³) X is the volume ratio of the transparent zirconia part to the zirconia sintered body, and Y is the volume ratio of the opaque zirconia part to the zirconia sintered body. Ma and Mb are densities of the HIP-treated body of each sintered body measured by the archimedes method. The HIP-treated body is a sintered body having a density equivalent to 100% relative density, and can be produced by the following method: the primary sintered body having a relative density of 97% or more and less than 100% was subjected to HIP treatment at 1500 ℃ under 150MPa for 1 hour using argon gas as a pressure medium.

The zirconia sintered body of the present embodiment has a biaxial bending strength of 300MPa or more. When the biaxial bending strength is less than 300MPa, the sheet is easily broken and the applications in which the sheet can be used are limited. In order to apply the zirconia sintered body of the present embodiment to a member requiring higher strength, the biaxial bending strength is preferably 350MPa or more, more preferably 400MPa or more, still more preferably 450MPa or more, still more preferably 500MPa or more, and still more preferably 600MPa or more. The biaxial bending strength of the present embodiment is 2000MPa or less, further 1000MPa or less, still further 900MPa or less, and still further 800MPa or less.

The biaxial bending strength in the present embodiment can be measured by a measurement method specified in ISO/DIS6872 for biaxial bending strength measurement.

In the measurement of biaxial bending strength, a plurality of supporting points (supports) for arranging a measurement sample are used. The support is disposed so that the interface surrounding the transparent zirconia portion or the opaque zirconia portion of the measurement sample falls within a circle (support circle) drawn by connecting the supports. The biaxial bending strength may be measured by loading a load having a size smaller than that of the interface on the measurement sample arranged so that the interface falls within the support circle at the center of gravity of the support diameter. For example, in the case of using a zirconia sintered body having a shape in which a disk-shaped transparent zirconia part having a diameter of 5mm is surrounded by an opaque zirconia part as a measurement sample, 3 or more support pieces (for example, 3 to 5-point ceramic balls) may be arranged so that the diameter of a support circle is larger than 5 mm. In the measurement, the weight may be applied to the center of gravity (center) of the support circle by a indenter having a diameter of less than 5 mm.

Fig. 1 is a schematic diagram showing measurement of biaxial bending strength, and is a diagram showing a zirconia sintered body disposed on a support. 100a shows a view of the zirconia sintered body when biaxial bending strength measurement is observed from the lower surface (i.e., the surface of the support member in contact with the zirconia sintered body), and 100b shows a cross section of the zirconia sintered body. The support members (110 a-110 c) are arranged so that the transparent zirconia part (101) falls inside the support circle. The zirconia sintered body is disposed so that the opaque zirconia part (102) is disposed on each support. The biaxial bending strength can be measured by applying a load (120) to the position of the center of gravity of the support circle.

In the present embodiment, the "transparent zirconia part" includes a transparent zirconia sintered body, and includes a zirconia sintered body having transparency. The transparent zirconia portion preferably contains a zirconia sintered body that can be visually recognized as having transparency, more preferably a colorless zirconia sintered body, and even more preferably a zirconia sintered body that has high transmittance of incident light, particularly high linear transmittance. The linear transmittance of the transparent zirconia portion is preferably 50% or more. When the linear transmittance is 50% or more, the film is easily visually recognized as transparent. The linear transmittance is more preferably 60% or more, and still more preferably 70% or more. Thus, the transparent zirconia part has aesthetic properties particularly suitable for applications such as a covering material for a timepiece and a display member for an electronic device. The linear transmittance of the transparent zirconia portion may be 75% or less.

In the present embodiment, the "linear transmittance" refers to a linear transmittance under a light source of D65 with a sample thickness of 1mm, and is a transmittance having a relationship of the following formula.

Ti＝Tt-Td

Tt: total light transmittance (%)

Td: diffuse transmittance (%)

Ti: linear transmittance (%)

The D65 illuminant refers to one of the illuminant standards specified by the Commission International de l' eclairage (CIE) for representing standard illuminant. The light source is light equivalent to natural sunlight. Therefore, when the zirconia sintered body of the present embodiment is set to a sample thickness of 1mm, a region having a linear transmittance of 50% or more, further 60% or more, and further 70% or more is observed, and it is confirmed that the zirconia sintered body of the present embodiment has a transparent zirconia part.

The transparent zirconia portion is preferably a zirconia sintered body containing zirconia having a cubic fluorite structure, more preferably a zirconia sintered body having zirconia having a cubic fluorite structure as a main phase, and even more preferably a zirconia sintered body composed of zirconia having a cubic fluorite structure.

The average crystal grain diameter of the zirconia sintered body contained in the transparent zirconia portion is preferably 5 μm or more and 200 μm or less. In the present embodiment, the average crystal grain diameter is the average diameter of the crystal grains of zirconia of the zirconia sintered body, and can be obtained by an intercept method from an observation image obtained by a Scanning Electron Microscope (SEM). The surface of the sintered body can be observed at a magnification of 15,000 times, 200 or more, preferably 250 ± 30 crystal grains of zirconia are extracted from the obtained SEM observation image, and the grain size is measured by an intercept method (k ═ 1.78) and averaged. Examples of the measurement of the average crystal grain include: the SEM observation images obtained under the following measurement conditions were analyzed by an intercept method using a commercially available analysis software (product name: interior scope) using a scanning electron microscope (device name: JSM-IT100, manufactured by JEOL Ltd.), and the average value of the obtained particle diameters was determined.

Acceleration voltage: 10kV

Measurement magnification: 400-10000 times of the total weight of the composition

The composition of the transparent zirconia part is arbitrary as long as it is a sintered body showing transparency. For example, the transparent zirconia portion may comprise titanium oxide (TiO) with a stabilizer₂) The zirconia of (2).

Examples of the stabilizer include yttrium oxide (Y)₂O₃) At least 1 of calcium oxide (CaO) and magnesium oxide (MgO), and preferably yttrium oxide.

The content of the stabilizer in the transparent zirconia portion is preferably an amount that can stabilize zirconia in a cubic fluorite structure. For example, when the stabilizing agent is yttria, the content of yttria may be 6 mol% or more and 12 mol% or less, preferably 7 mol% or more and 12 mol% or less, more preferably 8 mol% or more and 11 mol% or less, and further preferably 8 mol% or more and 10 mol% or less.

In the present embodiment, the content of the stabilizer is based on the amount of the stabilizer converted into an oxide relative to the stabilizer and zirconia (ZrO)₂) The ratio (% by mol) of the total of (A) and (B) is defined by { [ stabilizer (mol) ]]/[ zirconium oxide (mol) + stabilizer (mol)]The value obtained by the method of { X100 }. The oxides of the stabilizer may be converted into: yttrium oxide of Y₂O₃The content of the stabilizer (yttrium oxide content) in the zirconia sintered body containing calcium oxide as CaO and magnesium oxide as MgO and containing yttrium oxide as the stabilizer is represented by { [ Y ]₂O₃(mol)]/[ZrO₂(mol)+Y₂O₃(mol)]Find out (X100).

Since the transparency of the transparent zirconia part is easily increased, the content of titanium oxide in the transparent zirconia part is 3 mol% or more and 20 mol% or less, preferably 5 mol% or more and 15 mol% or less, and more preferably 8 mol% or more and 12 mol% or less.

In the present embodiment, the content of titanium oxide is titanium oxide (TiO)₂) The ratio (% by mol) of the stabilizer in terms of oxide to the total of zirconia and titania is defined by { [ titanium oxide (mol) ]]/[ zirconium oxide (mol) + stabilizer (mol) + titanium oxide (mol)]The value obtained by the method of { X100 }.

Transparent zirconia part except hafnium oxide (HfO)₂) And the like, and coloring elements and the like may be contained as long as transparency is not impaired. For example, the transparent zirconia part may be made of Al₂O₃The aluminum is contained in an amount of 0 to 0.1 mass% in terms of the content.

The "opaque zirconia part" includes an opaque zirconia sintered body, and includes a zirconia sintered body having no transparency. Further, the opaque zirconia portion preferably includes a zirconia sintered body that is not transparent to the naked eye, more preferably includes a colored zirconia sintered body, and still more preferably includes a zirconia sintered body having a low transmittance of incident light. In order to improve the visibility of the interface between the opaque zirconia portion and the transparent zirconia portion, the opaque zirconia portion preferably contains an achromatic zirconia sintered body.

The linear transmittance of the opaque zirconia portion is preferably less than 5%, more preferably less than 4%, further preferably less than 3%, and further more preferably less than 2%. When the zirconia sintered body has a linear transmittance of less than 5%, the body is easily visually opaque. When the incident light is totally reflected and/or the transmitted light is totally diffused, the linear transmittance of the zirconia sintered body is 0%. Therefore, the linear transmittance of the opaque zirconia portion is 0% or more. Therefore, when the zirconia sintered body of the present embodiment is set to a sample thickness of 1mm, it is possible to confirm that the zirconia sintered body has an opaque zirconia portion in addition to a region having a linear transmittance of less than 50%, further less than 10%, still further less than 5%, still further less than 4%, and still further less than 2%.

The opaque zirconia portion is preferably a zirconia sintered body containing zirconia having a tetragonal fluorite structure, more preferably a zirconia sintered body having zirconia having a tetragonal fluorite structure as a main phase, and even more preferably a zirconia sintered body composed of zirconia having a tetragonal fluorite structure.

The average crystal grain diameter of zirconia contained in the opaque zirconia portion is preferably 0.1 μm or more and 50 μm or less.

The composition of the opaque zirconia part may be any as long as it is a zirconia sintered body having no transparency. The opaque zirconia portion preferably contains a stabilizer and titania, and preferably contains zirconia containing a coloring element and the balance of the stabilizer and titania.

The stabilizer contained in the opaque zirconia portion includes at least 1 selected from yttria, calcia, and magnesia, and is preferably yttria.

The content of the stabilizer may be preferably an amount that stabilizes zirconia to a tetragonal fluorite structure. For example, when the stabilizing agent is yttria, the yttria content in the opaque zirconia portion may be 2 mol% or more and 6 mol% or less, preferably 2 mol% or more and 4 mol% or less, and more preferably 2.5 mol% or more and 3.5 mol% or less.

Since the mechanical strength tends to be high, the content of titanium oxide in the opaque zirconia portion is 1 mol% or more and 7 mol% or less, and preferably 1.5 mol% or more and 6 mol% or less.

In the zirconia sintered body of the present embodiment, the transparent zirconia portion and the opaque zirconia portion preferably contain zirconia containing a stabilizer and titania.

In the case where the transparent zirconia portion and the opaque zirconia portion each contain titania, the titania content in the opaque zirconia portion is preferably less than that in the transparent zirconia portion, and further, the difference in the titania content between the transparent zirconia portion and the opaque zirconia portion is preferably 2 mol% or more and 10 mol% or less, and more preferably 3 mol% or more and 7 mol% or less.

The opaque zirconia portion may have any color tone, and may be white, red, yellow, orange, pink, green, cyan, violet, gray, or black. The color tone having a higher sense of heaviness and a higher aesthetic quality includes at least any one of cyan and black, the general color tone includes any one selected from white, gray, and black, and the color tone having a decorative effect includes any one selected from red, yellow, orange, and pink.

In order to express such a color tone, the opaque zirconia portion preferably contains an element (coloring element) that gives a coloring effect to zirconia. Examples of the coloring element included in the opaque zirconia portion include at least 1 kind selected from transition metal elements, alkali metal elements, alkaline earth metal elements, aluminum (Al), silicon (Si), boron (B), phosphorus (P), germanium (Ge), and rare earth elements, preferably at least 1 kind selected from aluminum, nickel (Ni), cobalt (Co), manganese (Mn), iron (Fe), cerium (Ce), praseodymium (Pr), neodymium (Nd), europium (Eu), and erbium (Er), and more preferably 1 or more kinds selected from aluminum, cobalt, and iron. The sintered body of the present embodiment may be exemplified by a sintered body containing any one of the following groups as coloring elements: at least cobalt and iron; at least cobalt, iron and manganese; at least cobalt, iron and aluminum; at least cobalt, iron, aluminum and manganese.

The opaque zirconia portion may contain unavoidable impurities such as hafnium oxide, but preferably contains no zinc (Zn) and no chromium (Cr), and the contents of zinc and chromium may be 0 mass% or more and less than 0.1 mass%, further 0.05 mass% or less, and preferably 0.005 mass% or less (for example) of the detection limit in the conventional composition analysis. The total content of zinc and chromium is a content in terms of oxide, which is a content in terms of zinc oxide (ZnO) and a content in terms of chromium oxide (Cr)₂O₃) The ratio of the total mass of the latter to the mass of the opaque zirconia portion.

In order to make the interface between the transparent zirconia portion and the opaque zirconia portion easily and clearly visible, the opaque zirconia portion may be represented by L^*a^*b^*Lightness L of hue of color system^*Is 10 or less and has a hue a^*A hue b of-2.00 to 2.00^*Is-2.00 or more and 5.00 or less. Further, a preferable color lightness L of the opaque zirconia portion can be mentioned^*Is 0 to 9.0 inclusive, preferably 0 to 5.5 inclusive, more preferably 0 to less than 3.0, and has a hue a^*Is-3.00 or more and 2.00 or less, preferably-0.1 or more and 0.80 or less, more preferably-0.50 or more and 0.50 or less, color phase b^*Is-2.00 or more and 4.00 or less, preferably-1.50 or more and 2.50 or less, more preferably-1.00 or more and 1.00 or less.

L^*a^*b^*The color tone of the color system was obtained by measuring a sintered body having a surface roughness (Ra) of 0.02nm or less according to JIS Z8722. The color tone can be measured using a conventional color difference meter (e.g., Spectrophotometer SD 3000, manufactured by Nippon Denshoku industries Co., Ltd.). The color tone can be measured under the following conditions by using a white plate as a background (so-called white background measurement), for example.

Light source: d65 light source

The field angle: 10 degree

The measurement method comprises the following steps: SCE

The monoclinic ratio of the opaque zirconia portion is preferably 10% or less, more preferably 6.5% or less, further preferably 2% or less, and particularly preferably 1% or less. The monoclinic ratio is a value obtained from an XRD spectrum of the surface of the sintered body by the following formula.

Monoclinic rate (%) ═ I_m(111)+I_m(11-1)]×100

/[I_m(111)+I_m(11-1)+I_t(111)+I_c(111)]

In the above formula, I_m(111) Is the integrated intensity of the (111) plane of monoclinic zirconia, I_m(11-1) is the integrated intensity of the (11-1) plane of monoclinic zirconia, I_t(111) Is the integrated intensity of the (111) plane of the tetragonal zirconia, I_c(111) Is the integrated intensity of the (111) plane of the cubic zirconia. The XRD spectrum of the sintered body can be measured under the following conditions using a conventional XRD device (for example, a device name: RINT-UltimaIII, manufactured by RIGAKU).

Line 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

The obtained XRD spectrum is analyzed by using a commercially available analysis software (for example, RINT-ULTIMA III, manufactured by RIGAKU Co., Ltd.) to determine the peak intensity of each surface.

The average crystal grain diameter of zirconia contained in the opaque zirconia portion is preferably 3.0 μm or less, and more preferably 2.5 μm or less. Particularly preferred average crystal grain size is 0.3 μm or more and 2.5 μm or less, and further 0.5 μm or more and 1.3 μm or less.

Examples of the zirconia sintered body suitable for the opaque zirconia part include: comprises a solid solution containing cobalt and iron, the balance comprising zirconia, and cobalt converted to Co₃O₄And (c) and (d) iron is converted to Fe₂O₃A zirconia sintered body (hereinafter also referred to as "black zirconia sintered body") in which the total content of (a) is more than 0.1 mass% and less than 3.0 mass%.

The black zirconia sintered body occupies more than 5.0 μm in an element distribution image obtained by an electron probe microanalyzer²The proportion of the cobalt region (b) is preferably 15% or less, and more preferably 5% or less.

The black zirconia sintered body preferably contains at least 1 selected from vanadium oxide and titanium oxide, and more preferably contains titanium oxide.

The black zirconia sintered body preferably contains aluminum, and an aluminum content is 0.1 mass% or more and 3.0 mass% or less, preferably 0.1 mass% or more and 2.0 mass% or less, and more preferably 0.1 mass% or more and 1.0 mass% or less. The aluminum content is Al₂O₃The mass ratio of aluminum to the black zirconia sintered body was calculated.

The black zirconia sintered body may contain manganese, and the content of manganese is 0.1 mass% or more and 5.0 mass% or less, preferably 0.2 mass% or more and 3.0 mass% or less, and more preferably 0.3 mass% or more and 2.5 mass% or less. The manganese content is Mn₃O₄The converted mass ratio of manganese to the black zirconia sintered body.

The black zirconia sintered body may contain silica, and the silica content may be 0.1 to 5.0 mass%, preferably 0.2 mass%More than or equal to 3.0 mass%, more preferably 0.3 mass% or more and 2.5 mass% or less. The silicon dioxide content is SiO₂The converted mass ratio of silicon to the black zirconia sintered body.

For example, in the case where the sintered body contains zirconia containing cobalt, iron, manganese and aluminum and the balance of titania and yttria, the aluminum content (mass%) is determined by the following formula:

Al₂O₃(g)/{Y₂O₃(g)+ZrO₂(g)+TiO₂(g)+Fe₂O₃(g)+Co₃O₄(g)+Mn₃O₄(g)+Al₂O₃(g)}×100，

the manganese content (% by mass) was determined by the following formula:

Mn₃O₄(g)/{Y₂O₃(g)+ZrO₂(g)+TiO₂(g)+Fe₂O₃(g)+Co₃O₄(g)+Mn₃O₄(g)+Al₂O₃(g)}×100。

as a particularly preferable composition of the black zirconia sintered body, there can be mentioned: comprising Co₃O₄0.02 to 0.2 mass% in terms of cobalt and Fe₂O₃0.03 to 0.5 mass% of iron and Al₂O₃Zirconium oxide containing 0.1 to 20 mass% of aluminum, the balance of titanium oxide and yttrium oxide, the balance being 2 to 6 mol% and 2 to 5 mol% respectively; further examples are: comprising Co₃O₄0.02 to 0.2 mass% in terms of cobalt and Fe₂O₃0.03 to 0.5 mass% of iron and Al₂O₃0.1 to 2 mass% of aluminum, and the balance of zirconia containing 2 to 6 mol% of titanium oxide and 2 to 4 mol% of yttrium oxide.

Next, a method for producing the zirconia sintered body of the present embodiment will be described.

The zirconia sintered body of the present embodiment can be produced by a production method including the following sintering steps: a secondary molded body obtained by laminating a primary molded body of a raw material powder containing either a raw material powder for a transparent zirconia part or a raw material powder for an opaque zirconia part and a molded body containing the other raw material powder is sintered.

The molded body to be subjected to the sintering step is a primary molded body (hereinafter, also simply referred to as "primary molded body") of a raw material powder containing either a transparent zirconia portion or an opaque zirconia portion (hereinafter, also simply referred to as "opaque raw material") and a secondary molded body (hereinafter, also simply referred to as "secondary molded body") obtained by laminating a molded body containing the other raw material powder.

The primary molded body is either a molded body containing a transparent raw material (hereinafter also referred to as "transparent molded body") or a molded body containing an opaque raw material (hereinafter also referred to as "opaque molded body"). The secondary molded article is a molded article obtained by laminating a primary molded article and a molded article containing the other raw material powder, and includes a transparent molded article and an opaque molded article. In a preferred embodiment, the secondary molded body is a molded body in which a transparent molded body and an opaque molded body are joined. The terms "primary" and "secondary" in the molded article are used for convenience of indicating the state of lamination, and do not indicate the order of stacking.

The shape of each of the primary molded body and the secondary molded body is arbitrary, and may be the same as that of the intended sintered body in consideration of shrinkage due to sintering. Further, the secondary molded body may have the following structure: the primary molded body has at least either a convex shape or a concave shape, and molded bodies containing the other raw material powder are laminated so as to cover the structure.

The method for producing the primary molded body and the secondary molded body is arbitrary. As a molding method, the following method can be exemplified: first, one of a transparent material and an opaque material is filled in a mold, and then, after the other material is laminated on the former material, the former material is molded, thereby obtaining a primary molded body and a secondary molded body at the same time. Further, the following molding method can be exemplified: first, one raw material powder is filled in a mold and molded to prepare a primary molded body, and then, another raw material powder is laminated on the primary molded body to prepare a secondary molded body; the following molding methods may also be exemplified: one raw material powder is filled in a mold and molded to produce a primary molded body, and then the primary molded body is placed on the mold of the secondary molded body and the other raw material powder is laminated on the primary molded body to mold the secondary molded body.

The molding method of the primary molded body and the secondary molded body may be a known molding method, and may include 1 or more molding methods selected from uniaxial press molding, Cold Isostatic Press (CIP) treatment, cast molding, sheet molding and injection molding, preferably 1 or more selected from uniaxial press molding, CIP treatment and injection molding.

In the case where the molding method is uniaxial press molding, the uniaxial pressing conditions may be 20MPa or more and 70MPa or less; when the molding method is a CIP treatment, examples of the CIP treatment conditions include 150MPa or more and 250MPa or less; when the molding method is injection molding, examples of injection molding conditions include 50MPa to 150MPa, and more preferably 70MPa to 130 MPa.

The transparent raw material is a precursor of the transparent zirconia portion, while the opaque raw material is a precursor of the opaque zirconia portion. The transparent raw material and the opaque raw material are usually powders having different compositions from each other, and these raw material powders may have compositions that form a transparent zirconia sintered body and an opaque zirconia sintered body, respectively, by sintering.

The transparent raw material and the opaque raw material are preferably each a mixed powder containing a zirconia source, a stabilizer source, and a titania source, and more preferably each a mixed powder containing a zirconia source containing a stabilizer and a titania source. Further, the transparent material and the opaque material may contain at least any one of the coloring element sources.

The zirconia source is zirconia or a precursor thereof, preferably zirconia in a state in which a zirconia sol is fired, more preferably zirconia in a state in which a zirconia sol obtained by at least one of a hydrothermal synthesis method and a hydrolysis method is fired, and still more preferably zirconia in a state in which a zirconia sol obtained by a hydrolysis method is fired.

The stabilizer source is a stabilizer or a precursor thereof, and may be exemplified by 1 or more selected from stabilizing element-containing oxides, chlorides, and hydroxides. When the stabilizer is yttria, the stabilizer source (yttria source) may be at least 1 selected from yttria, yttrium chloride, and yttrium hydroxide, and is preferably at least one of yttria and yttrium chloride. In the case where the stabilizer is calcium oxide, the stabilizer source (calcium oxide source) may be at least 1 selected from the group consisting of calcium oxide, calcium chloride and calcium hydroxide, and preferably at least any one of calcium oxide and calcium chloride. In the case where the stabilizer is magnesium oxide, the stabilizer source (magnesium oxide source) may be at least 1 selected from magnesium oxide, magnesium chloride and magnesium hydroxide, and preferably at least any one of magnesium oxide and magnesium chloride.

The titanium oxide source is titanium oxide or a precursor thereof, and may be 1 or more selected from titanium oxide, titanium chloride, titanium hydroxide and titanium tetraisopropoxide, preferably at least one of titanium oxide and titanium chloride, and more preferably titanium oxide. More preferred examples of the titanium oxide source include those having a purity of 99.9% or more and a BET specific surface area of 10m²100m above/g²A titanium oxide powder having an average crystal grain diameter of 30nm or less and an average secondary particle diameter of 500nm or less, and more preferably a titanium oxide powder obtained by at least one of a sulfuric acid method and a vapor phase thermal decomposition method. The titania source preferably has a larger BET specific surface area than the zirconia source and the zirconia source containing the stabilizer.

The stabilizer-containing zirconia source is zirconia in which a stabilizer is dissolved in a solid solution, and examples thereof include 1 or more selected from yttria-containing zirconia, calcium oxide-containing zirconia, and magnesium oxide-containing zirconia, and preferably include zirconiaYttrium zirconium oxide. A preferable zirconia source containing yttria has a purity of 99.9% or more and a BET specific surface area of 5m²More than g and 20m²An yttria-containing zirconia powder having an average crystal grain diameter of 10nm to 50nm and an average secondary particle diameter of 100nm to 500nm, and more preferably an yttria-containing zirconia powder obtained by at least one of a hydrothermal synthesis method and a hydrolysis method.

The coloring element source is contained so that the zirconia portion can be given an arbitrary color. The coloring element source is a compound containing a coloring element, and may include 1 or more selected from an oxide, a hydroxide, an oxyhydroxide, a chloride, a sulfide, an acetate, a nitrate, and a sulfate of a coloring element, and preferably 1 or more selected from an oxide, a hydroxide, and an oxyhydroxide of a coloring element. When the coloring element is cobalt, the coloring element source (cobalt source) is a compound containing cobalt (Co), and examples thereof include compounds selected from cobaltosic oxide (Co)₃O₄) Cobalt (III) oxide (Co)₂O₃) Cobalt (II) oxide (CoO), cobalt oxyhydroxide (CoOOH), cobalt hydroxide (Co (OH)₂) Cobalt nitrate (Co (NO)₃)₂) Cobalt chloride (CoCl)₂) And cobalt sulfate (CoSO)₄) Preferably at least 1 selected from Co₃O₄、Co₂O₃At least 1 of CoO and CoOOH.

When the coloring element is iron, the coloring element source (iron source) is a compound containing iron (Fe), and examples thereof include iron (III, II) oxide (Fe)₃O₄) Iron (III) oxide (Fe)₂O₃) Iron (II) oxide (FeO), iron oxyhydroxide (FeOOH), iron hydroxide (FeOH), iron nitrate (Fe (NO)₃)₂) Iron chloride (FeCl) and iron sulfate (FeSO)₄) Preferably selected from Fe₃O₄、Fe₂O₃At least 1 of FeO and FeOOH.

When the coloring element is aluminum, the coloring element source (aluminum source) is a compound containing aluminum (Al), and examples thereof include compounds selected from aluminum oxide (Al)₂O₃) Hydrogen, hydrogenAlumina (Al (OH)₃) Aluminum chloride (AlCl)₃) Aluminum isopropoxide (C)₉H₂₁O₃Al) and aluminum nitrate (Al (NO)₃)₃) Preferably at least one of alumina and aluminum hydroxide.

When the coloring element is manganese, the coloring element source (manganese source) is a compound containing manganese (Mn), and may be selected from manganese oxide (MnO) and manganese dioxide (MnO)₂) Manganomanganic oxide (Mn)₃O₄) Manganese hydroxide (Mn (OH))₂) Manganese oxyhydroxide (MnOOH), manganese sulfate (MnSO)₄) Manganese nitrate (Mn (NO)₃)₂) And manganese chloride (MnCl)₂) Preferably 1 or more selected from manganese dioxide, trimanganese tetroxide and manganese hydroxide.

When the coloring element is silicon, the coloring element source (silicon source) is a compound containing silicon (Si), and includes at least 1 selected from colloidal silica, precipitated silica, amorphous silica, sodium silicate, tetraethyl orthosilicate, and silica powder, and preferably silica powder.

The content of the stabilizer in the transparent raw material is preferably an amount that stabilizes zirconia to a cubic fluorite structure by sintering. For example, when the stabilizing agent is yttria, the content of yttria may be 6 mol% or more and 12 mol% or less, preferably 7 mol% or more and 12 mol% or less, more preferably 8 mol% or more and 11 mol% or less, and further preferably 8 mol% or more and 10 mol% or less.

The content of titanium oxide in the transparent raw material is 3 mol% or more and 20 mol% or less, preferably 5 mol% or more and 15 mol% or less, and more preferably 8 mol% or more and 12 mol% or less.

The content of the stabilizer of the opaque raw material is preferably an amount that stabilizes zirconia into a tetragonal fluorite structure by sintering. For example, when the stabilizer is yttria, the content of yttria may be 2 mol% or more and 6 mol% or less, preferably 2 mol% or more and 4 mol% or less, and more preferably 2.5 mol% or more and 3.5 mol% or less.

The content of titanium oxide in the opaque material is 1 mol% or more and 7 mol% or less, preferably 1.5 mol% or more and 6 mol% or less.

The content of the coloring element source in the opaque material may be any content depending on the target color tone, and may be, for example, 0.01 mass% or more and 50 mass% or less, preferably 0.1 mass% or more and 20 mass% or less, and more preferably 0.3 mass% or more and 10 mass% or less. For example, as the coloring element source, there can be mentioned: cobalt content as Co₃O₄A ratio of the converted mass to the mass of the opaque raw material is 0.1 mass% or more and 5 mass% or less; the iron content being Fe₂O₃A ratio of the converted mass to the mass of the opaque raw material is 0.1 mass% or more and 5 mass% or less; a nickel content of 0.1 to 10 mass% in terms of a mass of NiO relative to a mass of the opaque raw material; the aluminum content is Al₂O₃The ratio of the converted mass to the mass of the opaque material is 0.1 mass% or more and 40 mass% or less.

In order to improve the flowability of the raw material powder, at least either one of the transparent raw material and the opaque raw material may contain an organic binder. When the organic binder is contained, the content of the organic binder in each raw material powder may be, for example, 25% by volume or more and 65% by volume or less, and further 35% by volume or more and 60% by volume or less.

The organic binder may be a known one usable in molding of ceramic powder, and may include, for example, at least 1 selected from acrylic resins, waxes and plasticizers. In the present embodiment, the acrylic resin may be a polymer containing at least either an acrylate residue unit or a methacrylate residue unit.

The transparent material and the opaque material are preferably in a state in which the materials such as a zirconia source are uniformly mixed. The mixing method of the raw materials is any mixing method, and at least either of dry mixing and wet mixing is sufficient, and wet mixing is preferable. The preferable wet mixing may be at least one of a ball mill and a stirring mill, and is preferably mixing by a ball mill using zirconia balls having a diameter of 1.0mm to 10.0 mm. In the case where the coloring element is contained, it is more preferable that the zirconia source and the coloring element source are mixed after the coloring element source is mixed.

In the case where the raw material powder contains an organic binder, the mixing method is arbitrary as long as the raw material powder and the organic binder can be uniformly mixed. As the mixing method, either one of heating kneading and wet mixing can be exemplified.

In the case of obtaining a zirconia sintered body having an opaque zirconia portion including a black zirconia sintered body, the opaque raw material (hereinafter also referred to as "black raw material") is preferably a mixed powder including a cobalt source, an iron source, and an alumina source, and the remainder including zirconia including yttria and titania, and is preferably a mixed powder of: comprising Co₃O₄0.02 to 0.2 mass% in terms of cobalt and Fe₂O₃0.03 to 0.5 mass% of iron and Al₂O₃0.1 to 30 mass% of aluminum in terms of the balance, and zirconia containing 2 to 6 mol% of titanium oxide and 2 to 4 mol% of yttrium oxide. The black raw material may contain at least either one of a manganese source and a silica source as needed, and may further contain a manganese source.

The ratio of the cobalt source to the iron source in the black raw material is arbitrary, and cobalt and iron in the black raw material are each converted into Co₃O₄And Fe₂O₃The latter weight ratio being Co₃O₄/(Co₃O₄+Fe₂O₃) The amount is preferably 0.10 or more and 0.99 or less, and more preferably 0.10 or more and 0.50 or less.

In the black raw material, the cobalt source, the iron source, and the aluminum source may be present in a state of containing a composite oxide of 2 or more selected from cobalt, iron, and aluminum. Examples of the composite oxide include CoFe₂O₄(cobalt ferrite) CoAl₂O₄Cobalt aluminate, FeAl₂O₄And FeAlO₃Preferably CoAl, and more than 1 of them₂O₄。

The difference in linear shrinkage between the transparent material and the opaque material (hereinafter also simply referred to as "difference in linear shrinkage") is preferably 5.0% or less. In general, since the thermal shrinkage behavior between transparent materials and opaque materials is significantly different from that between transparent materials or between opaque materials, defects are likely to occur when the transparent materials and the opaque materials are sintered together, and the yield is likely to be significantly reduced. On the other hand, in the present embodiment, since the difference in the linear shrinkage rate is 5.5% or less, and further 5.0% or less, defects are less likely to occur during sintering, and thus the yield is likely to be improved. The difference in linear shrinkage is any of 4.5% or less, 4.0% or less, 3.5% or less, 3.0% or less, 2.5% or less, and 2.0% or less. Since it is difficult to match the linear shrinkage rates of the raw material powders having different compositions, the difference in linear shrinkage rates is 0% or more, and more preferably 0.1% or more.

The "linear shrinkage ratio" in the present embodiment is one of indexes of thermal shrinkage behavior, and a rectangular parallelepiped sample (for example, a rectangular parallelepiped sample having a width of 30mm, a thickness of 3mm, and a length of 40 mm) (hereinafter, also referred to as a "rectangular parallelepiped sample") or a disk-shaped sample (for example, a disk-shaped sample having a diameter of 22mm and a thickness of 1 mm) (hereinafter, also referred to as a "disk sample") is subjected to a firing treatment as a measurement sample, and can be obtained from values before and after the firing treatment using the following formula.

< cuboid sample >

S₁＝(S_W+S_T+S_L)/3

In this case, the amount of the solvent to be used,

S_W＝100×{(L_w2-L_w1)/L_w1}

S_T＝100×{(L_T2-L_T1)/L_T1}

S_L＝100×{(L_L2-L_L1)/L_L1}。

furthermore, S₁Is the linear shrinkage (%) of the rectangular parallelepiped sample, S_WLinear shrinkage (%) of the width, L_w1Is the width (mm), L, of a rectangular parallelepiped sample before firing treatment_w2Is rectangular after firing treatmentWidth (mm) of the body sample, S_TIs the linear shrinkage (%) of the thickness, L_T1Is the thickness (mm), L, of a rectangular parallelepiped sample before firing treatment_T2Is the thickness (mm), S, of the rectangular parallelepiped sample after firing treatment_LIs the linear shrinkage (%) of the length, L_L1Is the length (mm), L, of a rectangular parallelepiped sample before firing treatment_L2The length (mm) of the rectangular parallelepiped sample after firing treatment. The width, thickness, and length may be measured using a vernier caliper.

< disc sample >

S₂＝(S_D+S_H)/2

In this case, the amount of the solvent to be used,

S_D＝100×{(L_D2-L_D1)/L_D1}

S_H＝100×{(L_H2-L_H1)/L_H1}。

furthermore, S₂Is the linear shrinkage (%) of the disc sample, S_DLinear shrinkage (%) of the diameter, L_D1The diameter (mm), L, of the disk sample before firing treatment_D2The diameter (mm), S, of the disk sample after the firing treatment_HIs the linear shrinkage (%) of the thickness, L_H1The thickness (mm), L, of the disk sample before firing treatment_H2The thickness (mm) of the disc sample after the firing treatment was measured. The diameter and thickness may be measured using a vernier caliper. The diameter may be an average value measured at 2 to 3 points.

The firing treatment in the measurement of the linear shrinkage ratio in the present embodiment may be performed in the air by a firing program in which the temperature rise rate is set to 100 ℃/h, the holding temperature is set to any one of 1300 ℃, 1400 ℃ or 1500 ℃, the holding time is set to 1 minute, and the temperature fall rate is set to 200 ℃/h.

In the present embodiment, the difference in linear shrinkage ratio (hereinafter also referred to as "Δ S") in the firing treatment at the holding temperature of 1300 ℃is preferable₍₁₃₀₀₎") and the difference in the linear shrinkage rate in the firing treatment at a holding temperature of 1400 ℃ (hereinafter also referred to as". DELTA.S ")₍₁₄₀₀₎") or a difference in linear shrinkage rate in the firing treatment at a holding temperature of 1500 ℃ (hereinafter also referred to as" holding temperature of 1500 ℃ ") (“△S₍₁₅₀₀₎") satisfies the difference in linear shrinkage, more preferably at least Δ S₍₁₃₀₀₎、△S₍₁₄₀₀₎And Δ S₍₁₅₀₀₎Maximum value of (d) (hereinafter also referred to as ". DELTA.S")_(MAX)") satisfies the above values, more preferably at least Δ S₍₁₄₀₀₎The above values are satisfied.

As preferred Δ S₍₁₃₀₀₎The content is 0% or more, preferably 0.1% or more, and 5.0% or less, preferably 4.5% or less, more preferably 3.5% or less, further preferably 3.0% or less, further more preferably 2.0% or less, further more preferably 1.0% or less; as preferred Δ S₍₁₄₀₀₎Examples thereof include 0% or more, preferably 0.5% or more, and 5.0% or less, preferably 4.5% or less, more preferably 4.0% or less, and further preferably 3.5% or less; further, as preferable Δ S₍₁₅₀₀₎Examples thereof include 0% or more, preferably 0.1% or more, and 3.0% or less, preferably 2.0% or less, more preferably 1.8% or less, further preferably 1.5% or less, and further more preferably 1.0% or less. Delta S₍₁₃₀₀₎And Δ S₍₁₅₀₀₎The difference is more preferably 0% or more and 4.0% or less, further 0% or more and 3.0% or less, further 0% or more and 2.5% or less, further 0% or more and 1.5% or less, further 0% or more and 1.0% or less, further 0.1% or more and 0.5% or less.

In the sintering step, the secondary molded body is sintered, whereby a zirconia sintered body in which the transparent zirconia portion and the opaque zirconia portion are joined can be obtained.

The sintering temperature of the sintered secondary molded body is preferably higher than 1100 ℃, more preferably 1200 ℃ or higher, and further preferably 1250 ℃ or higher. The sintering temperature is not particularly limited as long as it can be applied to a conventional sintering apparatus, and may be 1700 ℃ or lower, and further 1600 ℃ or lower.

Any sintering method can be applied to the sintering step, and for example, 1 or more selected from the group consisting of atmospheric pressure sintering, microwave sintering, and hot isostatic pressing (hereinafter also referred to as "HIP treatment") can be used. In order to suppress the generation of defects on the interface of the transparent zirconia part and the opaque zirconia part, in the sintering step, the sintering preferably includes at least the HIP treatment, more preferably the atmospheric pressure sintering and the HIP treatment. In the present embodiment, "atmospheric sintering" refers to a method of sintering a material to be fired without applying external pressure during firing. The atmospheric pressure sintered body can be obtained by atmospheric pressure sintering.

As a preferable sintering method, sintering is carried out under atmospheric pressure at 1300 ℃ to 1400 ℃ and then HIP treatment is carried out at 1450 ℃ to 1550 ℃. Thus, the zirconia sintered body of the present embodiment can be made into a HIP-treated body.

The conditions of the atmospheric pressure sintering other than the sintering temperature are arbitrary, the sintering atmosphere is either an oxidizing atmosphere or an atmospheric atmosphere, preferably an atmospheric atmosphere, and the sintering time is 30 minutes to 5 hours, preferably 1 hour to 3 hours.

The conditions of the HIP treatment other than the HIP treatment temperature are arbitrary, and an inert gas, preferably at least one of nitrogen gas and argon gas, is used as the pressure medium, the HIP pressure is 50MPa or more and 200MPa or less, and the HIP treatment time is 0.5 hours or more and 10 hours or less. The HIP treatment atmosphere is preferably an atmosphere other than an oxygen atmosphere, more preferably at least one of a reducing atmosphere and an inert atmosphere, and still more preferably a reducing atmosphere.

The HIP treatment preferably places the sample in HIP sintering under a reducing atmosphere, preferably in a container made of a reducing material. Generally, a reducing substance such as carbon is used as a constituent member such as a heating element of the HIP treatment apparatus. Therefore, even if an inert gas is used as the pressure medium, the atmosphere of the HIP treatment is likely to form an unstable atmosphere such as a weakly reducing atmosphere from an inert atmosphere. However, by placing the sample in HIP sintering in a reducing atmosphere, the zirconia sintered body of the present embodiment can be easily and stably obtained. The atmosphere in the HIP treatment, particularly the atmosphere in the vicinity of the sample in the HIP treatment, can be controlled by any method, and the sample can be easily placed in a container containing a reducing material. By selecting the material of the container in which the sample is disposed in the HIP treatment, the atmosphere in the vicinity of the sample can be stabilized. For example, by placing a sample in a container made of an oxide ceramic such as alumina, zirconia, or mullite, the sample can be placed in an inert atmosphere during HIP sintering. On the other hand, by disposing the sample in a container containing a reducing material such as carbon, the sample can be placed under a reducing atmosphere in the HIP treatment.

In the sintering step, after sintering, annealing treatment is preferably performed. Thereby, the linear transmittance of the transparent zirconia portion becomes higher. The conditions of the annealing treatment are arbitrary, and examples thereof include, for example, an oxygen atmosphere (for example, an atmospheric atmosphere), a treatment temperature of 850 ℃ to 950 ℃, and a treatment time of 0.5 to 2 hours.

The manufacturing method of the present embodiment may include a processing step of processing the zirconia sintered body into an arbitrary shape. By the processing, the transparent zirconia portion and the opaque zirconia portion can be exposed on the same surface, the surface can be made smoother, and fine correction of the shape and the like can be performed, and aesthetic properties according to the application use can be further imparted.

As the machining method, any method can be used, and for example, 1 or more selected from the group consisting of rotary disc machining, flat surface grinding, R grinding, and NC machining (numerical control machining) can be used. In addition, in order to further enhance gloss, polishing processing such as at least one of barrel polishing and R polishing may be exemplified.

Examples

The zirconia sintered body of the present disclosure is specifically described below by examples and comparative examples. However, the present disclosure is not limited to the following examples.

(Linear transmittance)

A disc-shaped sintered body having a thickness of 1mm and a diameter of 25mm was prepared, and both surfaces thereof were mirror-polished to a surface roughness Ra of 0.02 μm or less, and this was used as a measurement sample. The linear transmittance was measured using a haze meter (device name: NDH5000, manufactured by Nippon Denshoku Kogyo Co., Ltd.) with an incident light beam of D65 and a spot diameter of 15 mm.

(color tone)

The color tone of the opaque zirconia portion was measured by a method in accordance with JIS Z8722. For the measurement, a conventional color difference meter (apparatus name: Spectrophotometer SD 3000, manufactured by Nippon Denshoku industries Co., Ltd.) was used, and measurement was performed with a white plate as a background and a sample set thereon (white background measurement). The measurement conditions are as follows.

Light source: d65 light source

The field angle: 10 degree

The measurement method comprises the following steps: SCE mode (mode for removing specular reflection light and measuring diffuse reflection light)

The color tone of the opaque zirconia portion was measured by visual observation using a zirconia sintered body having a surface roughness Ra of 0.02 μm or less as a measurement sample.

(measurement of the difference in Linear shrinkage percentage)

A powder sample was pressure-molded with a mold having a pressure of 25MPa, and subjected to CIP treatment under a pressure of 200MPa to obtain a rectangular parallelepiped-shaped molded body having a width of 30mm, a thickness of 3mm and a length of 40mm, or a disc-shaped molded body having a diameter of 22mm and a thickness of 1mm, and the molded bodies were used as measurement samples. The width (L) of the test piece was measured on a rectangular parallelepiped sample using a vernier caliper_W1) Thickness (L)_T1) And length (L)_L1) The diameter (L) of the specimen was measured on a disc-shaped specimen_D1) And thickness (L)_H1). After the measurement, the molded article was subjected to firing treatment in the atmosphere using a conventional firing furnace (equipment name: SC-2025H, manufactured by MOTOYAMA) using a firing program of any of a temperature rise rate of 100 ℃/H, a holding temperature of 1300 ℃, 1400 ℃ or 1500 ℃, a holding time of 1 minute, and a temperature fall rate of 200 ℃/H. For the measurement samples after the firing treatment by the firing program set at each holding temperature, the width (L) of the rectangular parallelepiped sample was measured using a vernier caliper_W2) Thickness (L)_T2) And length (L)_L2) The diameter (L) of the specimen was measured on a disc-shaped specimen_D2) And thickness (L)_H2). The respective linear shrinkage rates were obtained from the obtained values, and the average value thereof was defined as the linear shrinkage rate (S) of the sample at each holding temperature₁,S₂). The difference in the linear shrinkage rates between the samples was referred to as the difference in the linear shrinkage rates.

(biaxial bending Strength)

A disc-shaped sintered body having a thickness of 1mm and a diameter of 25mm (or 12mm) was prepared, and the surface roughness (Ra) of both surfaces of the sintered body was mirror-polished to 0.02 μm or less to obtain a measurement sample. The biaxial bending strength was measured using the measurement sample according to the biaxial bending strength measurement specified in ISO/DIS 6872. In the biaxial bending strength measurement, in order to set the interface between the transparent zirconia portion and the opaque zirconia portion inside the support circle, 3-point supporters were disposed so that the diameter of the support circle became 22mm or 11mm in accordance with the shape of the measurement sample. The support member was measured by applying a load to the transparent zirconia part so that the transparent zirconia part was loaded with a zirconia ball having a ball diameter of 9.5 mm.

(EPMA measurement)

An element distribution image was obtained by observing a backscattered electron image using an EPMA apparatus (apparatus name: EPMA1610, manufactured by Shimadzu corporation) under the following conditions.

The measurement method comprises the following steps: wavelength dispersion type

Acceleration voltage: 15kV

Irradiation current: 300nA

Analysis area: 51.2 μm.times.51.2 μm

The number of fields of view: 3 fields of view

The obtained element distribution image was binarized using analytical software (product name: EPMA system ver.2.14, product of shimadzu corporation) attached to EPMA1610, and the number of regions in which the intensity of characteristic X-rays of cobalt or iron in the background was 1.5 times or more was counted. The Co distribution, the Fe distribution, the most frequent Co distribution and the most frequent Fe distribution are obtained according to the proportion of the number of the regions in the counted number of the regions.

The sintered body sample used was a disc-shaped sintered body having a thickness of 1mm and a diameter of 16mm and a surface roughness Ra of 0.02 μm or less.

Example 1

(transparent Material)

The BET specific surface area was set to 5.3m²Zirconia powder containing 10 mol% of yttria and a BET specific surface area of 20m²The titanium oxide powder was mixed in an ethanol solvent by ball mill using zirconia balls having a diameter of 10 mm. Ball mill mixing by pulverizing titanium oxide powder in ethanol solvent, further mixing with zirconia powder containing yttrium oxideAnd then the reaction is carried out. The mixed powder was dried in the air to obtain zirconia powder containing 10 mol% of yttria and 9.1 mol% of titania, which was used as a transparent raw material. The titanium (Ti) content of the titanium oxide contained in the transparent raw material is TiO₂The mass of titanium after conversion was 6.8 mass% based on the mass of the transparent raw material.

(opaque raw Material)

Alumina powder, iron oxide powder, cobalt oxide powder, 3 mol% yttria-containing zirconia powder, and titania powder were wet-mixed in an ethanol solvent using a zirconia ball mill to obtain a mixed powder containing 0.25 mass% of alumina, 0.16 mass% of iron oxide, and 0.04 mass% of cobalt oxide, with the remainder being zirconia containing 3 mol% yttria and 4.7 mol% titania. The mixed powder was dried at 110 ℃ in the air, and then sieved to obtain an opaque material (black material). Titanium (Ti) content of titanium oxide contained in the opaque raw material is TiO₂The ratio of the converted mass of titanium to the mass of the opaque raw material (hereinafter, also referred to as "titanium mass ratio") corresponds to 3.0 mass%.

(molded body)

A disc-shaped primary mold having a diameter of 25mm and a concavo-convex shape was filled with a transparent raw material, and uniaxial pressing was performed under a pressure of 25MPa to obtain a primary molded body composed of a disc-shaped transparent molded body having a thickness of 2mm and a diameter of 25 mm. The convex shape of the primary molded body was set as the above, and the molded body was placed in a disk-shaped secondary mold having a diameter of 50 mm. The opaque raw material is filled so that the upper side of the primary molded body is completely covered. Thereafter, the molded article was uniaxially pressed under a pressure of 50MPa to obtain a secondary molded article in which a transparent molded article and an opaque molded article were laminated, and then subjected to CIP treatment under a pressure of 200 MPa. Thus, a disk-shaped secondary molded body having a thickness of 3.5mm and a diameter of 50mm was obtained. Fig. 2 is a schematic view showing a cross section of a secondary molded body (200), showing a secondary molded body in which a transparent molded body and an opaque molded body are laminated, having the following structure: a primary molded body (201) composed of a transparent molded body is disposed in a secondary mold (210), and an opaque molded body (202) covers the exposed surface of the primary molded body.

(zirconia sintered body)

The obtained secondary molded body was subjected to atmospheric pressure sintering at a heating rate of 100 ℃ per hour, a sintering temperature of 1350 ℃ for 2 hours, and then subjected to HIP treatment at a temperature of 1500 ℃, a pressure of 150MPa, and a holding time of 1 hour in the air. After the HIP treatment, annealing treatment was performed at 900 ℃ for 8 hours in the air to obtain a sintered body. In the HIP treatment, argon gas having a purity of 99.9% was used as a pressure medium, and the sample was placed in a carbon container with a lid.

The annealed sintered body is subjected to cutting and polishing until the transparent zirconia portion and the opaque zirconia portion are exposed on both surfaces thereof. Thus, a disk-shaped zirconia sintered body having a thickness of 1.0mm, a transparent zirconia part and an opaque zirconia part, and the transparent zirconia part and the opaque zirconia part being exposed on the same surface was prepared as the zirconia sintered body of the present example.

Fig. 3 is a schematic diagram showing the external appearance of the front surface (300a) and the cross section (300b) of the zirconia sintered body of the present example after cutting and grinding. As shown in the front view (300a), the zirconia sintered body of the present example has a structure in which an opaque zirconia part (302) is disposed so as to surround a transparent zirconia part (301), and has a disk shape in which the transparent zirconia part (301) and the opaque zirconia part (302) are exposed on the same surface. Further, as shown in the sectional view (300b), the zirconia sintered body of the present example has a structure having a transparent zirconia portion continuous in the thickness direction. By virtue of the transparency of the transparent zirconia part, when the zirconia sintered body of the present example is disposed, it is possible to realize a function as a window material, and to visually recognize the design of the background thereof.

The annealed zirconia sintered body was subjected to composition analysis by EPMA. EPMA compositional analysis confirmed that cobalt was not contained in the transparent zirconia part of the zirconia sintered body in a region of 10 μm from the interface (detection limit or less).

In addition, the difference in linear shrinkage in the present example was confirmed to be Δ S₍₁₃₀₀₎0.8% and Delta S₍₁₄₀₀₎Is 3.0% and Δ S₍₁₅₀₀₎0.6% and Delta S_(MAX)Is 3.0%,. DELTA.S₍₁₃₀₀₎And Δ S₍₁₅₀₀₎The difference was 0.2%.

Examples 2 and 3

An opaque raw material (black raw material) was obtained by changing the mixing ratio of alumina powder, iron oxide powder, cobalt oxide powder, zirconia powder containing 3 mol% of yttria (or zirconia powder containing 4 mol% of yttria), and titania powder so as to have the following composition; using a disc-shaped primary mold having a diameter of 12mm and an irregular shape, a primary molded body comprising a disc-shaped transparent molded body having a thickness of 5mm and a diameter of 12mm was produced; a disc-shaped secondary molded article having a thickness of 4mm and a diameter of 25mm was obtained in the same manner as in example 1, except that this primary molded article was used. Except for the above-mentioned operation, the same method as in example 1 was carried out to obtain the zirconia sintered body of each example. In any of the examples, the titanium mass ratio was 3.0 mass%.

[ Table 1]

Examples 4 to 11

(transparent Material, opaque Material)

Zirconia powder containing 10 mol% of yttria and 9.1 mol% of titania obtained by the same method as in example 1 was used as a transparent raw material.

A mixed powder was obtained as an opaque raw material (black raw material) by the same method as in example 1 except that the mixing ratio of the alumina powder, the iron oxide powder, the cobalt oxide powder, the zirconia powder containing 3 mol% of yttria, and the titania powder was changed so as to have the following composition. The composition of the opaque starting material obtained is shown in the table below. With respect to the titanium mass ratio, examples 4 to 8 were 4.0 mass%, and examples 9 to 11 were 5.0 mass%.

[ Table 2]

(sintered body)

A primary molded article comprising a disc-shaped transparent molded article having a thickness of 5mm and a diameter of 12mm was produced using each opaque raw material and a disc-shaped primary mold having a concavo-convex shape and a diameter of 12mm, and a disc-shaped secondary molded article having a thickness of 4mm and a diameter of 23mm was obtained in the same manner as in example 1 except that this primary molded article was used. The obtained secondary molded body was subjected to the same method as in example 1 to obtain a zirconia sintered body of each example.

The obtained zirconia sintered bodies were each a disk-shaped zirconia sintered body having a thickness of 1.0mm and having a transparent zirconia part and an opaque zirconia part, the transparent zirconia part and the opaque zirconia part being exposed on the same surface. The results of measuring the color tone of the opaque zirconia parts of examples 2, 4 and 5 were each: lightness L^*0.74 and a hue a^*Is 0.05 and a hue b^*Is-0.20 (example 4); lightness L^*A hue a of 2.64^*0.65 and a hue b^*0.78 (example 6); lightness L^*A hue a of 6.75^*Is 1.33 and a hue b^*It was 2.66 (example 7).

Examples 12 to 15

Except that an opaque raw material (black raw material) was obtained by changing the mixing ratio of iron oxide powder, cobalt oxide powder, 3 mol% yttria-containing zirconia powder, and titania powder so as to have the following composition, the zirconia sintered body of each example was obtained by the same method as that of example 2. The titanium mass ratio was 3.0 mass%.

[ Table 3]

Examples 16 to 23

Except that an opaque material (black material) was obtained by changing the mixing ratio of alumina powder, iron oxide powder, cobalt oxide powder, zirconia powder containing 3 mol% of yttria (or zirconia powder containing 4 mol% of yttria), titanium oxide powder and trimanganese tetroxide powder so as to have the following composition, the zirconia sintered body of each example was obtained by the same method as that of example 2. The mass ratio of titanium was 3.0 mass% in example 16 and 4.0 mass% in examples 17 to 23.

[ Table 4]

Further, as a result of measuring the difference in linear shrinkage ratios for examples 17 to 19, Δ S in example 17 was the difference in linear shrinkage ratio₍₁₃₀₀₎4.1% and Delta S₍₁₄₀₀₎Is 5.2% and. DELTA.S₍₁₅₀₀₎1.9 percent; in example 18. DELTA.S₍₁₃₀₀₎4.9% and Delta S₍₁₄₀₀₎Is 4.8% and Δ S₍₁₅₀₀₎1.9 percent; Δ S in example 19₍₁₃₀₀₎5.9% and Delta S₍₁₄₀₀₎Is 5.0% and. DELTA.S₍₁₅₀₀₎The content was 1.9%.

Comparative example 1

According to Japanese patent application laid-open No. 2013-14471, a ceramic bonded body is obtained as follows.

(Black zirconia sintered body)

Black zirconia powder (product name: TZ-Black, manufactured by Tosoh corporation) was uniaxially press-molded under a pressure of 50MPa, and subjected to CIP treatment under a pressure of 200MPa to obtain a plate-shaped molded article having a longitudinal dimension of 30mm and a lateral dimension of 40 mm. The obtained molded body was sintered at normal pressure, and then the obtained zirconia sintered body was machined to obtain a black zirconia sintered body having a rectangular hollow portion with a thickness of 1.15mm, a vertical length of 14mm, and a horizontal length of 22mm, and a frame shape with a thickness of 1.15mm, a vertical length of 28mm, and a horizontal length of 36 mm.

(transparent zirconia sintered body)

In zirconia powder containing 10 mol% of yttria (product name: TZ-10YS, manufactured by Tosoh corporation), 10 mol% of high purity titania powder was added to zirconia, and the resultant was mixed with zirconia balls having a diameter of 10mm in an ethanol solvent for 72 hours by a ball mill, and then dried to obtain a raw material powder. The raw material powder was uniaxially pressed under a pressure of 50MPa and subjected to CIP treatment under a pressure of 200MPa to obtain a plate-like molded article having a thickness of 2mm, a longitudinal length of 50mm and a lateral length of 40 mm.

The obtained plate-like molded body was subjected to atmospheric sintering at a heating rate of 100 ℃ per hour, a sintering temperature of 1350 ℃ and a sintering time of 2 hours in the atmosphere to obtain an atmospheric sintered body. Next, the atmospheric pressure sintered body was subjected to HIP treatment at a temperature of 1650 ℃, a pressure of 150MPa, and a holding time of 1 hour. In the HIP treatment, argon gas having a purity of 99.9% was used as a pressure medium, and the sample was placed in a carbon container with a lid. After HIP sintering, annealing treatment was performed at 1000 ℃ for 1 hour in the atmosphere to obtain a transparent zirconia sintered body.

(ceramic bond)

A transparent zirconia sintered body was disposed inside a black zirconia sintered body, and HIP treatment was performed at a pressure of 150MPa, a holding temperature of 1200 ℃ and a holding time of 1 hour, thereby obtaining a ceramic joined body. The HIP treatment was carried out at a holding temperature of 1200 ℃ under a pressure of 150MPa for a holding time of 1 hour, and a sample was placed in an alumina container using argon (Ar) having a purity of 99.9% as a pressure medium. After the HIP treatment, the obtained HIP sintered body was annealed at 1000 ℃ for 1 hour in the air to obtain a zirconia bonded body of the present comparative example.

The results of the biaxial bending strength measurement of these examples and comparative examples are shown in the following table.

[ Table 5]

The zirconia sintered bodies of the examples all had a biaxial bending strength of 350MPa or more, a biaxial bending strength of more than 400MPa, and a biaxial bending strength of 600MPa or more, whereas the zirconia joined body of comparative example 1 had a biaxial bending strength of less than 250 MPa. In addition, when the failure source of the zirconia bonded body of comparative example 1 was confirmed, it was confirmed that fracture started from the portion (bonding surface) where the black zirconia sintered body and the translucent zirconia sintered body were in contact.

Synthesis example 1 (transparent zirconia sintered body)

A primary molded body was obtained in the same manner as in example 1. A transparent zirconia sintered body was produced in the same manner as in example 1, except that the obtained primary molded body was used instead of the secondary molded body.

The obtained zirconia sintered body exhibited the same transparency as the transparent zirconia part of the zirconia sintered body of example 1, and had a linear transmittance of 69% and an average crystal grain diameter of 25 μm.

The biaxial bending strength of the transparent zirconia sintered body was 181MPa, which is a value lower than that of the zirconia sintered bodies of examples.

Synthesis example 2 (Black zirconia sintered body)

A primary molded body was obtained in the same manner as in example 1, except that the raw material powder of the opaque zirconia portion was used instead of the raw material powder of the transparent zirconia portion. A black zirconia sintered body was produced in the same manner as in example 1, except that the obtained primary molded body was used instead of the secondary molded body.

The obtained zirconia sintered body exhibited the same color tone as the opaque zirconia portion of the zirconia sintered body of example 1, and had a linear transmittance of 0% (detection limit or less), an average crystal grain diameter of 1.1 μm, and a monoclinic phase ratio of 0%.

Examples 24 to 26

Except that an opaque raw material (black raw material) was obtained by changing the mixing ratio of alumina powder, iron oxide powder, cobalt oxide powder, zirconia powder containing 4 mol% of yttria, titania powder and silica powder so as to have the following composition, the zirconia sintered body of each example was obtained by the same method as that of example 2. The titanium mass ratio was 4.0 mass%.

[ Table 6]

Example 27

(transparent Material)

By the same method as in example 1, zirconia powder containing 10 mol% of yttria and 9.1 mol% of titania was obtained. Titanium (Ti) in the titanium oxide contained in the mixed powder is TiO₂The mass of titanium after conversion was 6.8 mass% based on the mass of the mixed powder. This powder was mixed with an organic binder containing an acrylic resin to prepare a composition, which was used as a transparent raw material in this example.

(opaque raw Material)

By the same method as in example 1, a mixed powder containing 0.25 mass% of alumina, 0.16 mass% of iron oxide, and 0.04 mass% of cobalt oxide, and the balance being zirconia containing 3 mol% of yttrium oxide and 4.7 mol% of titanium oxide was obtained. The titanium (Ti) content of the titanium oxide contained in the mixed powder is TiO₂The mass of titanium after conversion was 3.0 mass% based on the mass of the mixed powder. This mixed powder was mixed with an organic binder containing an acrylic resin to prepare a composition, which was used as an opaque material in this example.

(molded body)

A transparent raw material was injection-molded in a primary mold to obtain a primary molded body having an uneven shape and comprising a disc-shaped transparent molded body having a thickness of 2mm and a diameter of 25 mm. The resulting primary molded article was placed in a disc-shaped secondary mold having a diameter of 50mm so that the uneven shape of the primary molded article faced upward. An opaque raw material was injection-molded on the primary molded body so as to cover the entire upper surface (exposed surface) of the primary molded body, thereby obtaining a disc-shaped secondary molded body having a thickness of 3.5mm and a diameter of 50mm, in which a transparent molded body and an opaque molded body were laminated.

(zirconia sintered body)

Except for using the obtained secondary molded body, the atmospheric pressure sintering, the HIP treatment, the annealing treatment and the working were carried out by the same method as in example 1 to obtain the zirconia sintered body of the present example.

The zirconia sintered body of the present example was a disk-shaped sintered body having a thickness of 1mm, and the transparent zirconia portion and the opaque zirconia portion were exposed on the same surface.

The specifications, claims, drawings and abstract of the specification of japanese patent application No. 2019-058458, filed on 26.3.2019 and japanese patent application No. 2020-025331, filed on 18.2.2020 are incorporated herein by reference in their entirety as disclosures of the specification of the present disclosure.

Description of the reference numerals

100a,100b,200a,200 b: zirconia sintered body

101,301: transparent zirconia part

102,302: opaque zirconia portion

110a,110b,110 c: support piece

120: load weight

200: secondary molding

201: primary molded body (transparent molded body)

202: opaque shaped bodies

210: secondary die