阅读说明：本技术 陶瓷构件 (Ceramic component ) 是由 胜勇人 于 2018-10-17 设计创作，主要内容包括：本发明提供一种陶瓷构件,该陶瓷构件由La、AE和Mn的复合氧化物构成,AE(i)为Ca、或者(ii)包含Ca且还包含Sr和Ba中的至少1种,Sr和Br的总量相对于Ca、Sr和Br的总和为5mol％以下,其表面的晶系为单斜晶系。(The present invention provides a ceramic member comprising a composite oxide of L a, AE and Mn, wherein AE (i) is Ca or (ii) contains Ca and also contains at least 1 of Sr and Ba, the total amount of Sr and Br is 5 mol% or less with respect to the total of Ca, Sr and Br, and the crystal system of the surface thereof is monoclinic.)

1. A ceramic member composed of a composite oxide of L a, AE and Mn,

AE (i) is Ca, or (ii) contains Ca and also contains at least 1 of Sr and Ba, the total amount of Sr and Br is 5 mol% or less relative to the total of Ca, Sr and Br,

the crystal system of the surface of the ceramic member is monoclinic.

2. The ceramic member according to claim 1, wherein the composite oxide has a composition represented by the following formula (I),

La_1-x-yAE_yMnO₃

in the formula:

AE (i) is Ca, or (ii) contains Ca and also contains at least 1 of Sr and Ba, the total amount of Sr and Br is 5 mol% or less relative to the total of Ca, Sr and Br,

x satisfies 0< x <0.20,

y satisfies 0< y ≦ 0.10.

3. The ceramic member according to claim 1, wherein the composite oxide is a composite oxide of L a, AE and Mn,

AE (i) is Ca, or (ii) contains Ca and also contains at least 1 of Sr and Ba, the total amount of Sr and Br is 5 mol% or less relative to the total of Ca, Sr and Br,

the sum of the molar fraction of L a and the molar fraction of AE is less than 100 parts by mole and 80 parts by mole or more per 100 parts by mole of Mn,

the molar fraction of AE contained is more than 0 molar fraction and 10 molar fractions or less with respect to 100 molar fractions of Mn.

4. A ceramic member composed of a composite oxide of L a, AE and Mn,

AE (i) is Ca, or (ii) contains Ca and also contains at least 1 of Sr and Ba, the total amount of Sr and Br is 5 mol% or less relative to the total of Ca, Sr and Br,

the ceramic member had peaks at 32.5 ° and 32.7 ° 2 θ in X-ray diffraction analysis using a CuK α radiation source.

5. The ceramic member according to claim 4, wherein the composite oxide has a composition represented by the following formula (I),

La_1-x-yAE_yMnO₃

in the formula:

AE (i) is Ca, or (ii) contains Ca and also contains at least 1 of Sr and Ba, the total amount of Sr and Br is 5 mol% or less relative to the total of Ca, Sr and Br,

x satisfies 0< x <0.20,

y satisfies 0< y ≦ 0.10.

6. The ceramic member according to claim 5, wherein the composite oxide is a composite oxide of L a, AE and Mn,

AE (i) is Ca, or (ii) contains Ca and also contains at least 1 of Sr and Ba, the total amount of Sr and Br is 5 mol% or less relative to the total of Ca, Sr and Br,

the sum of the molar fraction of L a and the molar fraction of AE is less than 100 parts by mole and 80 parts by mole or more per 100 parts by mole of Mn,

the molar fraction of AE contained is more than 0 molar fraction and 10 molar fractions or less with respect to 100 molar fractions of Mn.

7. The ceramic member according to any one of claims 4 to 6, wherein a ratio of a peak intensity of 32.7 ° 2 θ to a peak intensity of 32.5 ° 2 θ is greater than 1.

8. The ceramic member according to any one of claims 1 to 7, wherein a crystal system of the surface is different from a crystal system of the central portion.

9. The ceramic member according to claim 8, wherein the crystal system of the surface is monoclinic and the crystal system of the central portion is orthorhombic.

10. The ceramic member according to any one of claims 1 to 9, which is an element body of an electronic component.

11. An electronic component comprising the element assembly according to claim 10 and an electrode formed on a surface of the element assembly.

12. The electronic component according to claim 11, wherein a square of an IV characteristic correlation coefficient r is 0.9995 or more.

13. The electronic component according to claim 11 or 12, which is used as a thermistor element for suppressing an inrush current.

14. A method for producing a ceramic member composed of a composite oxide of L a, AE and Mn,

the manufacturing method comprises the following steps:

a step of calcining L a source, an AE source and a Mn source to obtain a sintered body, wherein AE (i) is Ca or (ii) contains Ca and also contains at least 1 of Sr and Ba, and the total amount of Sr and Br is 5 mol% or less with respect to the total amount of Ca, Sr and Br;

removing at least a part of the surface of the obtained sintered body;

and annealing the sintered body from which at least a part of the surface has been removed at 900 ℃ or higher in the presence of oxygen.

Technical Field

The present invention relates to a ceramic member and a method for manufacturing the same.

Background

In recent years, electric vehicles, hybrid vehicles, and the like, which have become widespread, use a large number of modules and engines that handle large currents. In these modules and the like, a surge current is generated when the power is turned on (or when the engine is started), and if an excessive surge current flows into the modules and the like, the electronic components, ICs, and the like inside the modules may be damaged, and therefore, countermeasures against this need to be taken. The use of a thermistor element as a suppressor for such a surge current is being studied.

When a thermistor element is used, a surge current generated at the time of starting an engine of an electric vehicle is several hundred a, and thus excellent surge current resistance is required, and high reliability is required because it is required to operate at a relatively high temperature, for example, 120 to 250 ℃. Further, when the resistance of the element itself is high, sufficient electric power cannot be supplied to the engine, which causes battery consumption, and therefore, the resistance of the element itself needs to be reduced. Therefore, as the thermistor material, a material having low resistance and rapidly decreasing resistance in the vicinity of 100 to 150 ℃ (i.e., a material having a large B constant) is preferably used.

Conventionally, as a thermistor element for suppressing a surge current, an NTC (Negative temperature coefficient) thermistor has been known. However, NTC thermistors have the following difficulties: the element having a small resistivity has a resistance change between a low-temperature state and a high-temperature state that is not sufficiently large (i.e., a B constant is small), and has a large power loss due to a residual resistance during a steady-state current flowing period (on state, high-temperature state). There are also the following problems: the resistivity of the element having a sufficiently large change in resistance (i.e., B constant) between the low-temperature state and the high-temperature state is large, and the element size is increased in order to reduce the element resistance. This is because there is generally a correlation between the resistivity of the conductive material and the B constant, and if the resistivity is reduced, the B constant becomes small, and it is difficult to achieve a low resistivity and a high B constant.

Therefore, use of CTR (Critical Temperature Resistor) as a thermistor element for suppressing surge current is being studied. CTR has a characteristic of showing a rapid decrease in resistance at a certain temperature or temperature range when the temperature is increased (hereinafter, abbreviated as "CTR characteristic"), and has a B constant extremely larger than that of an NTC thermistor in which the resistance gradually decreases with an increase in temperature.

As a ceramic material having CTR characteristics, a ceramic material characterized by having a chemical property is proposedFormula R1_1-xR2_xBaMn₂O₆In the structure shown in the figure, the structure,

(1) when R1 is composed of Nd, R2 is composed of at least 1 of Sm, Eu and Gd, x is more than or equal to 0.05 and less than or equal to 1.0,

(2) when R1 is Nd, R2 is at least 1 of Tb, Dy, Ho, Er and Y, x is more than or equal to 0.05 and less than or equal to 0.8,

(3) when R1 is composed of at least 1 of Sm, Eu and Gd and R2 is composed of at least 1 of Tb, Dy, Ho and Y, x is more than or equal to 0 and less than or equal to 0.4,

(4) when R1 is composed of at least 1 of Sm, Eu and Gd, and R2 is composed of at least 1 of Sm, Eu and Gd which is not selected as R1 and is the remainder, x is 0. ltoreq. x.ltoreq.1.0 (patent document 1).

The ceramic material described in patent document 1 is an a-site-ordered Mn compound in which a rare earth element and barium entering an a site of a perovskite structure are ordered, and exhibits CTR characteristics. Patent document 1 describes the following: this ceramic material exhibits a rapid resistance change at around 100 ℃, as shown in fig. 2 of the document, for example, and is suitable for constituting a thermistor element for suppressing a surge current.

Disclosure of Invention

Problems to be solved by the invention

The present inventors have conducted studies on the above ceramic material described in patent document 1, and as a result, they have found that the material is actually low in resistance and exhibits a rapid change in resistance, but the resistance is increased by a thermal cycle test and a high-temperature standing test, and therefore, in order to obtain a ceramic material having a small specific resistance, a high B constant, and excellent thermal cycle resistance and high-temperature resistance (in other words, excellent reliability), they focused on the use of L a, AE (AE is at least 1 of Ca, Sr, and Ba), and Mn.

As a result of further continuing research, excellent electrical characteristics, in particular, IV (current-voltage) characteristics are required in the thermistor element, and the present inventors have found that the above-described composite oxide has a problem of deterioration of IV characteristics in the case of being produced into a thermistor element by a conventional production method.

Means for solving the problems

The present inventors have found that the IV characteristics can be improved by annealing a ceramic member composed of L a, AE (about AE, Ca, or a composite oxide containing Ca and at least 1 of Sr and Ba) and Mn.

According to the 1 st gist of the present disclosure, there is provided a ceramic member composed of a composite oxide of L a, AE and Mn,

AE (i) is Ca, or (ii) contains Ca and also contains at least 1 of Sr and Ba, the total amount of Sr and Br is 5 mol% or less relative to the total of Ca, Sr and Br,

the crystal system of the surface of the ceramic member is monoclinic.

According to the 2 nd gist of the present disclosure, there is provided a ceramic member composed of a composite oxide of L a, AE and Mn,

AE (i) is Ca, or (ii) contains Ca and also contains at least 1 of Sr and Ba, the total amount of Sr and Br is 5 mol% or less relative to the total of Ca, Sr and Br,

the ceramic member had peaks at 32.5 ° and 32.7 ° 2 θ in X-ray diffraction analysis using a CuK α radiation source.

According to the gist of the 3 rd aspect of the present disclosure, there is provided an electronic component having the element assembly of the ceramic member and an electrode formed on a surface of the element assembly.

According to the gist of the 4 th aspect of the present disclosure, there is provided a method for producing a ceramic member composed of a composite oxide of L a, AE and Mn,

the manufacturing method comprises the following steps:

a step of calcining L a source, AE source and Mn source to obtain a sintered body (here, AE (i) is Ca, or (ii) contains Ca and at least 1 of Sr and Ba, and the total amount of Sr and Br is 5 mol% or less with respect to the total of Ca, Sr, and Br);

removing at least a part of the surface of the obtained sintered body;

and annealing the sintered body from which at least a part of the surface has been removed at 900 ℃ or higher in the presence of oxygen.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present disclosure, a ceramic member excellent in electrical characteristics can be provided by annealing a member composed of L a, AE (about AE, Ca, or a composite oxide containing Ca and at least 1 of Sr and Ba) and Mn.

Drawings

Fig. 1 shows the IV characteristics of the test specimens in the examples.

Fig. 2 shows XRD spectra of the samples in the examples.

Detailed Description

The ceramic member of the present invention and an electronic component using the same will be described in detail below.

The ceramic member of the present invention is composed of a ceramic material that can be understood as a composite oxide of L a, AE and Mn, wherein AE (i) is Ca, or (ii) at least 1 selected from Sr and Ba in addition to Ca, and the total amount of Sr and Br is 5 mol% or less with respect to the total amount of Ca, Sr and Br.

In one embodiment, the ceramic material is a composite oxide having a composition represented by the following formula (I):

La_1-x-yAE_yMnO₃

[ in the formula:

AE (i) is Ca, or (ii) contains Ca and also contains at least 1 of Sr and Ba, the total amount of Sr and Br is 5 mol% or less relative to the total of Ca, Sr and Br,

x satisfies 0< x <0.20,

y satisfies 0< y ≦ 0.10. ].

In a preferred embodiment, in formula (I), x satisfies 0< x <0.20, and y satisfies 0.03< y < 0.10.

By having the above composition, the ceramic member of the present disclosure has a lower resistivity, exhibits a rapid resistance change due to a temperature rise, and also has a higher B constant and excellent reliability (heat cycle resistance).

In the formula (I) representing the composition of the composite oxide, the oxygen amount is defined as 3, and the oxygen amount may be non-stoichiometric. That is, in the above formula, the oxygen amount may be slightly less than 3 or slightly more than 3 depending on the kind of AE or x and y. This amount of oxygen is also acceptable in the present invention.

In another embodiment, the ceramic material is a composite oxide of L a, AE and Mn,

AE (i) is Ca, or (ii) contains Ca and also contains at least 1 of Sr and Ba, the total amount of Sr and Br is 5 mol% or less relative to the total of Ca, Sr and Br,

the sum of the molar fraction of L a and the molar fraction of AE is less than 100 parts by mole and 80 parts by mole or more per 100 parts by mole of Mn,

the molar fraction of AE contained is more than 0 molar fraction and 10 molar fractions or less with respect to 100 molar fractions of Mn.

In a preferred embodiment, the sum of the molar fraction of L a and the molar fraction of AE is less than 100 parts by mole and 80 parts by mole or more based on 100 parts by mole of Mn,

the molar fraction of AE contained is more than 3 molar fractions and less than 10 molar fractions with respect to 100 molar fractions of Mn.

By having the above composition, the ceramic member of the present disclosure has a lower resistivity, exhibits a rapid resistance change due to a temperature rise, and also has a higher B constant and excellent reliability (heat cycle resistance).

In these embodiments, when AE is Ca and at least 1 selected from Sr and Ba, the total amount of Sr and Br is preferably 3 mol% or less, more preferably 1 mol% or less, and may be 0.5 mol% or less, for example, with respect to the total of Ca, Sr, and Br. The lower limit of the total amount of Sr and Br is not particularly limited, and may be, for example, 0.01 mol% or more and 0.1 mol% or more. AE is preferably Ca.

When the temperature of the ceramic material is increased, the resistivity is lowered.

The ceramic material has a low specific resistance, particularly at room temperature. More specifically, the ceramic material has a resistivity at 25 ℃ of, for example, 10 Ω · cm or less, preferably 5 Ω · cm or less, more preferably 2 Ω · cm or less, and still more preferably 1 Ω · cm or less. This improves the degree of freedom in designing the size (shape) of the element, and makes it easier to manufacture the element. This improves the response to the inrush current, and effectively suppresses the inrush current.

As described above, the ceramic material exhibits a large resistance change due to a temperature change. The magnitude of the resistance change due to the temperature change can be evaluated using a B constant calculated from the following equation as an index.

B constant ═ ln (R)₁/R₂)/(1/T₁-1/T₂)…(1)

In the formula, R₁And R₂Respectively represents T₁And T₂Resistance value (Ω) at the temperature (K).

The ceramic material was measured for resistance values at 5 ℃ intervals, and B constants at 25 ℃ and 100 ℃ were T₂＝100℃、T₁The B constant obtained based on the above formula at 25 ℃ is, for example, 1500K or more, preferably 2000K or more, and more preferably 2400K or more. This can effectively suppress the surge current and effectively reduce the power loss due to the residual resistance during the steady-state current flowing period (on state). Hereinafter, in the present specification, the term "B constant" means T₁25 ℃ (298K) and T₂100 ℃ (373K) B constant based on formula (1) above.

In a preferred embodiment, the ceramic material has a resistivity of 5 Ω · cm or less and a B constant of 1500K or more, preferably a resistivity of 2 Ω · cm or less and a B constant of 2000K or more, more preferably a B constant of 2400K or more in the case of a resistivity exceeding 1 Ω · cm and 2 Ω · cm or less, and a B constant of 2000K or more in the case of a resistivity of 1 Ω · cm or less.

The ceramic material can effectively prevent resistance change before and after a thermal cycle test, exhibits high thermal cycle resistance, and can realize excellent reliability. More specifically, even when a thermal cycle test is performed at a temperature ranging from-25 ℃ to 240 ℃, for example, the rate of change in resistance between before and after can be made 10% or less. Also, excellent resistance can be achieved against high temperature storage at 250 ℃.

The ceramic material can be produced by appropriately combining methods known in the art of composite oxides.

In general, it can be produced by weighing a material containing calcium, strontium, or barium and containing oxygen (for example, an oxide, a carbonate, a hydroxide, and the like, hereinafter the same applies) as an AE source (i.e., a Ca source, an Sr source, or a Ba source), a material containing lanthanum and oxygen as an L a source, and a material containing manganese and oxygen as an Mn source at a desired ratio, mixing them (appropriately together with a binder and the like), and calcining them.

The ceramic member of the present disclosure is composed of the above ceramic material.

In one embodiment, the crystal system of the surface of the ceramic member of the present disclosure is a monoclinic system. By having a monoclinic crystal structure on the surface, in the case where an electrode is formed, ohmic contact can be formed at the interface of the ceramic member and the electrode, and the electrical characteristics are improved.

The crystal system of the surface of the ceramic member can be confirmed by X-ray diffraction analysis.

The "surface" of the ceramic member means a depth penetrated by at least X-rays from the CuK α radiation source, and includes a region from the outermost surface to 10 μm, for example.

In another mode, the ceramic member of the present disclosure has peaks at 32.5 ° and 32.7 ° when the surface of the ceramic member is analyzed by X-ray diffraction analysis using a CuK α radiation source.

The X-ray diffraction analysis described above can be performed using RINT-K (manufactured by Rigaku Corporation).

In a preferred embodiment, the ratio (I2/I1) of the peak intensity at 32.7 ° 2 θ (hereinafter also referred to as "I2") to the peak intensity at 32.5 ° 2 θ (hereinafter also referred to as "I1") is greater than 1.00. I2/I1 is preferably 1.40 or more, more preferably 2.00 or more.

In one embodiment, the surface of the ceramic member has a crystal system different from that of the central portion.

In a preferred embodiment, the surface of the ceramic member has a monoclinic crystal system, and the central portion has an orthorhombic crystal system. Note that the phrase "the crystal system of the surface is monoclinic" and "the crystal system of the central portion is orthorhombic" does not mean that the crystal system in this region is completely monoclinic and completely orthorhombic, respectively, but means that the crystal system is mainly monoclinic and orthorhombic. For example, 55% or more, preferably 70% or more, more preferably 90% or more, further preferably 95% or more, and further more preferably substantially all, for example, 99.0% or more or 99.5% or more, of the crystals in this region may have a predetermined crystal system.

Here, the "central portion" of the ceramic member refers to a portion located at a distance of 100 μm or more, preferably 300 μm or more, from the outermost surface of the ceramic member, and typically may be a portion near the center of gravity of the ceramic member.

The shape of the ceramic member of the present disclosure is not particularly limited, and may be a shape suitable for an electronic element, for example, a rectangular parallelepiped shape, a disc shape, a plate shape, or the like.

The ceramic member of the present disclosure can be used as a member of an electronic component. In particular, the ceramic member of the present disclosure exhibits ntc (negative Temperature coefficient) characteristics, and therefore can be suitably used as a member for a thermistor element, for example, as an element body.

Accordingly, the present disclosure discloses the above ceramic member as an element body of an electronic component. The present disclosure also discloses an electronic component comprising the element assembly of the present disclosure and an electrode formed on a surface of the element assembly. Preferably, the present disclosure discloses an electronic component including the element body of the present disclosure and at least 2 electrodes formed to sandwich at least a part of the element body.

In one embodiment, the electrode of the electronic component of the present disclosure is preferably provided in a portion of the surface of the element body having a monoclinic crystal structure.

In one embodiment, the electrode of the electronic component of the present disclosure is preferably provided in a portion of the surface of the element body having peaks at 32.5 ° and 32.7 ° 2 θ.

In a preferred embodiment, the electrode of the electronic component of the present disclosure is preferably provided in a portion of the surface of the element body in which a ratio of a peak intensity at 2 θ of 32.7 ° to a peak intensity at 2 θ of 32.5 ° is greater than 1.

By providing the electrode in a portion having a monoclinic crystal structure, a portion having peaks at 32.5 ° and 32.7 ° 2 θ, or a portion having a ratio of the peak intensity at 32.7 ° 2 θ to the peak intensity at 32.5 ° 2 θ, as described above, which is greater than 1, ohmic contact can be formed at the interface between the electrode and the element body, and electrical characteristics, such as IV characteristics (current-voltage characteristics), can be improved.

In one embodiment, the square of the IV characteristic correlation coefficient r of the electronic component of the present disclosure is 0.9993 or more, preferably 0.9995 or more, more preferably 0.9999 or more, and still more preferably 1.0000.

Here, the IV characteristic correlation coefficient r can be obtained by the following equation when the voltage (V) is on the x-axis and the current (I) is on the y-axis.

The material constituting the electrode is not particularly limited, and is preferably made of a conductive material, and is preferably made of 1 or 2 or more metal materials selected from Au, Ag, Pd, Ni, Cu, and Sn. In a preferred mode, the material is Ag. By using Ag, ohmic contact at the boundary between the electrode and the element body can be more favorably formed.

The electronic component of the present disclosure has low resistance and excellent electrical characteristics, and therefore can be suitably used as a surge current suppressing element.

Hereinafter, a method for manufacturing an electronic component of the present disclosure will be described.

The electronic component of the present disclosure can be obtained by obtaining a body as a ceramic member of the present disclosure and forming electrodes on the surface thereof.

Specifically, the ceramic member of the present disclosure can be obtained as follows.

L a source, AE source and Mn source are prepared, AE is at least 1 of Ca, Sr and Ba, typically, L a is prepared in relation to L a₂O₃As for Ca, CaCO is prepared₃As for Sr, SrCO is prepared₃As for Ba, BaCO was prepared₃。

These were weighed and mixed so as to have a desired composition, and molded into a desired shape to obtain an uncalcined element body. The method of mixing and molding is not particularly limited, and a conventional method for producing a ceramic body can be used. For example, the molding can be performed by mixing the slurry with a dispersant, a binder, or the like, forming the slurry into a green sheet by a doctor blade method or the like, and laminating the green sheet. Alternatively, a pressing method may be used to obtain an uncalcined green body.

Subsequently, the obtained green body is calcined to obtain a sintered body. The calcination may be carried out in the atmosphere.

The calcination conditions are not particularly limited, and for example, a temperature of 1250 ℃ to 1300 ℃ and a calcination time of 1 hour to 10 hours are preferable.

Next, a part of the surface of the obtained sintered body was removed, and the sintered body was formed into a desired shape. The method for removing is not particularly limited, but polishing, particularly lapping, is preferable.

Subsequently, the treated sintered body is annealed. By performing the annealing treatment, the crystal system of the surface treated in the surface removing step can be monoclinic.

The annealing treatment is performed in an oxygen atmosphere, preferably in the air.

The annealing treatment is performed at a temperature of 900 ℃ or higher. By annealing at 900 ℃ or higher, the crystal system of the surface of the element body can be made monoclinic.

In this manner, a ceramic body as the ceramic member of the present disclosure can be obtained.

Accordingly, the present disclosure provides a method for manufacturing a ceramic member composed of a composite oxide of L a, AE and Mn,

the manufacturing method comprises the following steps:

a step of obtaining a sintered body obtained by calcining L a source, an AE source, and a Mn source (here, AE (i) is Ca, or (ii) contains Ca and also at least 1 of Sr and Ba, and the total amount of Sr and Br is 5 mol% or less with respect to the total of Ca, Sr, and Br);

removing at least a part of the surface of the obtained sintered body;

and annealing the sintered body from which at least a part of the surface has been removed at 900 ℃ or higher in the presence of oxygen.

The electronic component of the present disclosure can be obtained by forming a pair of electrodes on the surface of the obtained element body.

The method for forming the electrode is not particularly limited, and for example, CVD method, plating, electroless plating, vapor deposition, sputtering, and baking of conductive paste can be used, and baking of conductive paste is preferably used.

The electronic component thus obtained has excellent electrical characteristics, particularly IV characteristics, because ohmic contact is formed at the interface between the electrode and the element body.