JP5931542B2 - Firing member made of zirconia sintered body - Google Patents

Description

  The present invention relates to a firing member made of a zirconia sintered body having excellent corrosion resistance and durability.

  In the firing of piezoelectric materials, dielectrics, and magnetic materials, which are electronic component materials, various methods have been improved and developed for the firing process in order to suppress the composition variation by minimizing the evaporation components of these materials to be fired. It is being advanced. In particular, high-performance electronic component materials mounted on information devices (PCs, mobile phones, personal digital assistants, etc.) that have made remarkable progress in recent years require precise composition control. There is a demand for a ceramic sintered body that is more excellent in corrosion resistance and durability. Above all, zirconia that has higher corrosion resistance to PbO than alumina and magnesia is used in the firing process of electronic parts materials such as piezoelectrics and dielectrics containing PbO. It has been.

  For example, an inexpensive and versatile refractory is one of them. However, since the refractory contains many pores, there is a problem in that corrosion resistance is inferior, for example, a fired body component easily permeates and reacts with the pores. In addition, the two-layered firing member in which the surface of the substrate made of alumina, mullite, cordierite, etc. is coated with a zirconia layer has various improvements to prevent the zirconia layer from peeling off. Has been proposed. However, when repeatedly used over a long period of time, the problem of peeling caused by the difference in thermal expansion between the zirconia layer and the substrate is unavoidable, and there is a problem that the fired body component penetrates into the peeled portion and the corrosion resistance deteriorates. . Thus, even if it is zirconia having high corrosion resistance, a porous body containing pores or a two-layer structure in which a zirconia layer is formed on the surface of a substrate is a process for firing a highly functional electronic component material in terms of corrosion resistance. Therefore, a dense zirconia sintered body excellent in corrosion resistance tended to be employed.

Many dense zirconia sintered bodies using Y ₂ O ₃ , CaO, MgO, CeO _{2 and the} like as stabilizers have been proposed so far. For example, in Patent Documents 1 and 2, A zirconia sintered body having excellent corrosion resistance and durability mainly composed of cubic zirconia is disclosed using at least one selected from the group consisting of Y ₂ O ₃ and CaO as a stabilizer. These have corrosion resistance and durability that can be used in conventional electronic component material applications, but they have sufficient corrosion resistance and durability for highly functional electronic component materials that require precise composition control. It wasn't. In particular, in the case of a body to be fired containing PbO, there is a problem that PbO penetrates into the member side and precise composition control of the body to be fired becomes impossible, resulting in poor corrosion resistance. Moreover, when repeatedly used, PbO permeation progresses and a layer in which PbO is segregated at a high concentration is formed on the surface side of the member. Due to the difference in thermal expansion between this layer and the inside of the member, deformation or cracks occur in the member. As a result, there is a problem that durability is lowered.

Patent Document 3 discloses a cubic zirconia sintered body excellent in ion conductivity, mechanical properties, and heat resistance using one or more of niobium and a niobium-based substance as a zirconia stabilizer. Has been. However, niobium pentoxide (Nb ₂ O ₅ ), which is one of the niobium-based materials, has a low effect as a stabilizer, so that it easily undergoes phase transition to monoclinic crystals by repeating heating and cooling several times. Due to the volume expansion accompanying the phase transition, there was a problem that deformation and cracks occurred in a short period of time and durability was lowered. Patent Document 3 describes that the cubic structure is stable in the entire temperature range from a low temperature range to a high temperature range, but in fact, thermal stability that can be used for firing highly functional electronic component materials. It was not inferior in durability. Further, it is described that niobium or a niobium-based substance can act as a sintering aid due to the presence of zirconia grain boundaries and improve mechanical properties, but niobium present in zirconia grain boundaries. Alternatively, the niobium-based material, or the second phase formed by the reaction of niobium or the niobium-based material with other components penetrates into the body to be fired or reacts with the material to be fired. Therefore, it was impossible to control the composition, and the corrosion resistance and durability were inferior.

  As described above, dense zirconia sintered bodies made of various cubic zirconia have been proposed so far, but corrosion resistance capable of precise composition control of the body to be fired, and over a long period of time. None of them have durability that can be used repeatedly, and they were not fully satisfactory as firing members used for firing highly functional electronic component materials.

JP 2004-315293 A JP 2005-82429 A Japanese Patent Laid-Open No. 1-108162

An object of the present invention is to provide a member for firing comprising a zirconia sintered body having corrosion resistance and durability superior to those of a conventional dense zirconia sintered body.
The excellent corrosion resistance in the present invention means that the depth of penetration of PbO in the fired body component into the zirconia sintered body in contact with the fired body is extremely shallow, and the zirconia sintered body The components inside do not penetrate into the body to be fired or react with the components of the body to be fired. The excellent durability means that the zirconia sintered body is not deformed, cracked or cracked when repeatedly used over a long period of time.
In addition, the firing member made of a zirconia sintered body as referred to in the present invention is a setter, container, covering powder and jigs used for firing electronic component materials, calcining synthesis of raw material powder for electronic component materials, and the like. It means a firing container to be used.

The above problem is solved by the following invention.
“(A) Y ₂ O ₃ which is a zirconia stabilizer is contained in an amount of 6 to 12 mol% based on zirconia, and (b) the molar ratio of Nb ₂ O ₅ and Y ₂ O ₃ is 0.03 to 0.3. In the zirconia sintered body in the range of 30, (c) is composed of a zirconia single phase having no second phase as a crystal phase, (d) the zirconia crystal phase is 95% by volume or more of cubic zirconia, (e) The total amount of inevitable impurities is 0.3% by weight or less, the SiO ₂ content is 0.03% by weight or less, (f) the porosity is 0.5% or less, and (g) the average crystal grain size is 3 to 3%. 30 μm, (h) A firing member comprising a zirconia sintered body, wherein the ratio of the minimum crystal grain size to the average crystal grain size is 0.05 or more. ”

  ADVANTAGE OF THE INVENTION According to this invention, the member for baking consisting of the zirconia sintered compact which has the corrosion resistance and durability superior to the conventional dense zirconia sintered compact can be provided. In particular, for a sintered body containing PbO, the depth at which PbO in the sintered body penetrates into the zirconia sintered body is extremely shallow, and the components in the zirconia sintered body penetrate into the fired body. Or has excellent corrosion resistance that does not react with the component to be fired. In addition, when used repeatedly over a long period of time, the zirconia sintered body has excellent durability that does not cause deformation, cracks, cracks and the like. Therefore, it is suitable for firing containers and setters for high-functional electronic component materials that do not contain PbO, as well as firing containers used for calcining synthesis of ceramic powders and firing of molded bodies, metal melting crucibles, glass melting It can also be effectively used in applications that require corrosion resistance and durability, such as containers for slag, containers for melting slag, and crucibles for growing single crystals.

Hereinafter, the present invention will be described in detail.
As a result of intensive studies in view of the above-mentioned present situation, the present inventors have found that the zirconia sintered body as a firing member is simply cubic zirconia in order to realize excellent corrosion resistance and durability. Therefore, it is not sufficient to control the sintering density, the crystal grain size, the amount of impurities, etc., and it is important to include a specific amount of Nb ₂ O ₅ in the stabilizer in combination with these requirements. I found out.
In other words, when a stabilizer is added to zirconia, the cation of the stabilizer substitutes for the zirconium ion and enters the cation lattice position, so that oxygen deficiency is generally formed to maintain electrical neutrality. Although it is known, it has been found from the research of the present inventors that PbO in the fired body permeates into the member side as the zirconia sintered body having more oxygen vacancies and the corrosion resistance and durability are lowered. is there.

As an example, in Patent Document 3 using Nb ₂ O ₅ as a stabilizer, a metal oxide (Y ₂ O ₃ , MgO, CaO) having a lower valence than that of zirconia is solidified in order to increase ion conductivity. Although it is disclosed that oxygen can be deficient and a large number of oxygen ion vacancies (oxygen vacancies) can be introduced by dissolving, the corrosion resistance and durability are remarkably low due to the large number of oxygen vacancies. It could not be used as a firing member.
Therefore, the present inventors have determined that it is important to reduce oxygen vacancies in order to obtain a zirconia sintered body having excellent corrosion resistance and durability, and as a result of intensive research, as a result of intensive research, If Nb ₂ O ₅ of an oxide composed of a cation having a high valence is contained in a very small amount with respect to the stabilizer, and the total amount thereof is completely dissolved in the zirconia crystal, the stabilizer It was found that the oxygen deficiency formed by can be reduced. At the same time, it consists of a zirconia single phase in which the second phase does not exist as a crystal phase, and this zirconia crystal phase is mainly composed of cubic zirconia, and by controlling the amount of impurities, porosity and average crystal grain size, Corrosion resistance and durability were drastically improved compared to the cubic zirconia sintered body, and a firing member made of a zirconia sintered body that can be sufficiently used for firing highly functional electronic component materials was completed.

Next, each component of the present invention will be described.
(A) in the present invention that it contains 6 to 12 mol% with respect to the a _Y 2 _{O 3} is a stabilizer of zirconia zirconia, 6-12 and _Y 2 _{O 3} is a stabilizer of zirconia relative to the zirconia It is necessary to contain it in mol%, preferably 7-11 mol%. Normally the ZrO ₂ in the raw materials, but contains a small amount of HfO _2, the total amount of ZrO ₂ and HfO _2, including the HfO ₂ amount and ZrO ₂ amount.
Conventionally, Y ₂ O ₃ , MgO, CaO, CeO _{2 and the} like have been used as stabilizers for zirconia, but those using MgO, CaO, CeO _{2 and the} like other than Y ₂ O ₃ are in the zirconia crystal phase. Since the thermal stability is not satisfactory, the excellent corrosion resistance and durability aimed by the present invention cannot be achieved. Therefore, in the present invention, it is necessary to use Y ₂ O ₃ as a stabilizer.
When the content of Y ₂ O ₃ is less than 6 mol%, monoclinic zirconia increases as the zirconia crystal phase, and cubic zirconia decreases, resulting in deterioration of corrosion resistance and durability. When the content of Y ₂ O ₃ exceeds 12 mol%, surplus Y ₂ O ₃ that could not be dissolved in zirconia reacts with Nb ₂ O _5, and this reaction compound (for example, Y ₃ NbO ₇ , YNbO ₄ ) is present as the second phase in the zirconia sintered body, and this reacts with the body to be fired to lower the corrosion resistance and durability.

(B) Mb ratio of Nb ₂ O ₅ and Y ₂ O ₃ (Nb ₂ O ₅ / Y ₂ O ₃ ) is in the range of 0.03 to 0.30 In the present invention, the stabilizer Y ₂ O ₃ In order to reduce oxygen vacancies in the zirconia sintered body formed by the above, it is necessary to contain a specific amount of Nb ₂ O ₅ with respect to Y ₂ O ₃ . Therefore, the molar ratio of Nb ₂ O ₅ and Y ₂ O ₃ is controlled in the range of 0.03 to 0.30, preferably 0.05 to 0.25.
When the molar ratio is less than 0.03, since the amount of Nb ₂ O _{5 with} respect to Y ₂ O ₃ is small, oxygen deficiency of the zirconia sintered body cannot be reduced, and corrosion resistance and durability are lowered. When the molar ratio exceeds 0.30, excess Nb ₂ O ₅ that could not be dissolved in the zirconia crystal reacts with ZrO ₂ or Y ₂ O _3, and this reaction compound (for example, Zr ₆ Nb ₂ O ₁₇ , Y ₃ NbO ₇ , YNbO ₄ ) are present as the second phase, and this reacts with the body to be fired, thereby reducing corrosion resistance and durability. Moreover, when the amount of Nb ₂ O ₅ added exceeds a predetermined amount, the zirconia crystal phase becomes unstable, so that monoclinic and tetragonal zirconia increases and cubic zirconia decreases, and corrosion resistance and durability Decreases.
Further, when the specific amount of Nb ₂ O ₅ is contained in Y ₂ O ₃ , the entire amount of Nb ₂ O ₅ can be completely dissolved in the zirconia crystal. When the entire amount of Nb ₂ O ₅ is not dissolved in the zirconia crystal, the second phase is generated by the excess Nb ₂ O ₅ , and therefore, by confirming the presence of the second phase, the solid phase of Nb ₂ O ₅ is confirmed. The dissolved state can be confirmed.

(C) The point which consists of a zirconia single phase in which a 2nd phase does not exist as a crystal phase In this invention, it needs to consist of a zirconia single phase in which a 2nd phase does not exist as a crystal phase.
When the second phase other than zirconia is present, corrosion resistance and durability are lowered.
In the present invention, the absence of the second phase means that, in X-ray diffraction, X-ray source: CuKα, output: 40 kV / 40 mA, divergence slit: 1 °, scattering slit: 1 °, light receiving slit: 0.15 mm , Scan speed: 3.0 ° / min, scan axis: 2θ / θ, scan range: 10 to 70 °, monochrome light receiving slit: 0.8 mm, counter: scintillation counter, monochromator: automatic monochromator In this case, it means a level where no diffraction peak other than zirconia is detected. For the X-ray diffraction measurement, a sample obtained by mirror finishing the sintered body is used.

(D) The point that the zirconia crystal phase is 95% by volume or more of cubic zirconia In the present invention, the zirconia crystal phase needs to be 95% by volume or more of cubic zirconia.
If cubic zirconia is less than 95% by volume, the monolithic and tetragonal zirconia is contained in the zirconia-based sintered body, so the volume associated with the phase transition of the zirconia crystal phase when heated and cooled. Due to the expansion, deformation and cracks occur, and the durability decreases. And the to-be-fired body component osmose | permeates the crack which generate | occur | produced, and corrosion resistance also falls.
The content of cubic, tetragonal and monoclinic zirconia in the present invention is determined by X-ray diffraction using a sample having a sintered body surface as a mirror surface and diffraction angles of 27 to 33 ° and 72 to 75. It can be measured from a scanning range of 5 ° and obtained from the following equation.

X-ray diffraction conditions are as follows: X-ray source: CuKα, output: 40 kV / 40 mA, divergence slit: 1/2 ° (diffraction angle 27-33 °), 1 ° (diffraction angle: 72-75.5 °), Scattering slit: 1/2 ° (diffraction angle 27-33 °), 1 ° (diffraction angle: 72-75.5 °), light-receiving slit: 0.15 mm, scan speed: 0.5 ° / min, scan axis: 2θ / θ, monochrome light receiving slit: 0.8 mm, counter: scintillation counter, monochromator: automatic monochromator.
In the present invention, the acceptable content of tetragonal zirconia is 3% by volume or less, and the acceptable content of monoclinic zirconia is 2% by volume or less.

(E) The point that the total amount of inevitable impurities is 0.3% by weight or less and the SiO ₂ content is 0.03% by weight or less The inevitable impurities in the present invention are mixed from the raw materials used and the manufacturing process. It is an impurity and refers to Al ₂ O ₃ , SiO ₂ , Na ₂ O, K ₂ O, TiO _{2 and the} like. The total amount of these inevitable impurities is 0.3% by weight or less, preferably 0.2% by weight or less.
When the total amount exceeds 0.3% by weight, many glass phases and second phases are formed in the zirconia grain boundaries, and the glass phases and second phases react with the object to be fired, resulting in corrosion resistance and durability. descend.
The lower limit of the total amount is about 0.1% by weight in the current raw materials and manufacturing process.
Among the inevitable impurities, SiO ₂ reacts easily with the object to be fired to lower the corrosion resistance and durability, or forms a lot of glass phase and second phase at the zirconia grain boundary to significantly increase the corrosion resistance and durability. It becomes a factor to reduce. Therefore, the content of SiO ₂ is set to 0.03% by weight or less. The lower limit is about 0.01% by weight in the current raw materials and manufacturing process.

(F) Point that porosity is 0.5% or less In the present invention, the porosity needs to be 0.5% or less, preferably 0.3% or less.
When the porosity exceeds 0.5%, the pores of the sintered body increase, and the fired body component penetrates into the pores, resulting in a decrease in corrosion resistance and durability. The lower limit of the porosity is about 0.01%. In addition, the porosity in this invention means an open porosity, and a measurement is performed based on JISR1634.

(G) The point that an average crystal grain diameter is 3-30 micrometers In this invention, the average crystal grain diameter of a zirconia sintered compact needs to be 3-30 micrometers, Preferably it is 5-25 micrometers.
When the average crystal grain size is less than 3 μm, the interfacial area of zirconia crystal grains increases, so that the fired body component penetrates into the increased grain boundaries and the corrosion resistance and durability are lowered. In addition, if the average crystal grain size exceeds 30 μm, the corrosion resistance does not decrease, but the thermal shock resistance decreases, which is not preferable. The average crystal grain size in the present invention is a value measured by the following method. .
The surface of the sintered body is mirror-finished using a diamond grindstone and abrasive grains, the obtained mirror surface is subjected to thermal etching, and observed with a scanning electron microscope at a magnification capable of observing 100 or more zirconia crystals in the field of view. , Take a photo. The major axis and minor axis of the crystal particles are measured from the obtained photograph, and the particle diameter of one crystal particle is determined as particle diameter = (major axis + minor axis) / 2. Thus, the particle diameter of 100 crystal particles is calculated | required randomly, and let the average value be an average crystal grain diameter.

(H) The ratio between the minimum crystal grain size and the average crystal grain size (minimum crystal grain size / average crystal grain size) is 0.05 or more In the present invention, the ratio between the minimum crystal grain size and the average crystal grain size is: It needs to be 0.05 or more, preferably 0.08 or more. The larger this value, the smaller the difference between the minimum crystal grain size and the average crystal grain size.
If the ratio is less than 0.05, the difference between the minimum crystal grain size and the average crystal grain size is greatly widened, so that many fine zirconia crystals are present in the sintered body, and the corrosion resistance is lowered. In addition, deformation occurs in a short period of time during repeated use, and durability is also reduced. The upper limit of the ratio is about 0.40.

The value measured by the following method is used for the minimum crystal grain size in the present invention.
The surface of the sintered body is mirror-finished using a diamond grindstone and abrasive grains, the obtained mirror surface is subjected to thermal etching, and observed with a scanning electron microscope at a magnification capable of observing 100 or more zirconia crystals in the field of view. , Take a photo. The major axis and minor axis of the crystal particles are measured from the obtained photograph, and the particle diameter of one crystal particle is determined as particle diameter = (major axis + minor axis) / 2. Thus, the particle diameter of 100 crystal particles is obtained at random, and the particle diameter showing the minimum value among the measured 100 particle diameters is set as the minimum crystal particle diameter.
The minimum crystal grain size / average crystal grain size is determined from the minimum crystal grain size thus measured and the average crystal grain size measured in (g) described above.

The zirconia sintered body and the firing member comprising the same in the present invention can be produced by various methods, and examples thereof will be described.
A zirconia raw material powder having a purity of 99.7% by weight or more and an average particle size of 10 μm or less is used. When the purity is less than 99.7% by weight, since the amount of impurities contained in the raw material powder is large, the amount of impurities in the sintered body is also increased, which is not preferable because corrosion resistance and durability are lowered. On the other hand, when the average particle diameter exceeds 10 μm, the processing time for pulverization, mixing and dispersion becomes long, and a large amount of impurities due to wear from the pulverizer is mixed, so that the corrosion resistance and durability are deteriorated. The lower limit of the average particle diameter is about 3 μm.

A Y ₂ O ₃ raw material powder having a purity of 99.7% by weight or more and an average particle size of 5 μm or less is used. When the purity is less than 99.7% by weight, since the amount of impurities contained in the raw material powder is large, the amount of impurities in the sintered body is also increased, which is not preferable because corrosion resistance and durability are lowered. On the other hand, when the average particle diameter exceeds 5 μm, the Y ₂ O ₃ raw material powder is coarse, so mixing and dispersion with other raw material powders become insufficient, and monoclinic zirconia increases in the sintered body, which is not preferable. . The lower limit of the average particle diameter is about 0.5 μm.

Y ₂ O ₃ used as a stabilizer may be added in the form of a compound such as a hydroxide. In that case, zirconia and Y ₂ O ₃ raw materials are used in advance so that a predetermined amount of Y ₂ O ₃ is obtained. Is mixed by dry mixing or wet mixing, dried, and then synthesized at 1000 to 1400 ° C. Incidentally, it may be omitted even if the synthesis is the case of using Y ₂ O ₃ is in the form of oxides.
Further, an aqueous solution of a zirconia compound (for example, zirconium oxychloride) and an aqueous solution of an yttrium compound (for example, yttrium chloride) are uniformly mixed and hydrolyzed so that the content of zirconia and Y ₂ O ₃ becomes a predetermined molar ratio. Thus, after obtaining hydrate, dehydration and drying, calcining at 400 to 1200 ° C. to obtain a powder with few impurities can be employed.

As the Nb ₂ O ₅ raw material powder, one having a purity of 99.7% by weight or more and an average particle diameter of 5 μm or less is used. When the purity is less than 99.7% by weight, since the amount of impurities contained in the raw material powder is large, the amount of impurities in the sintered body is also increased, which is not preferable because corrosion resistance and durability are lowered. Further, when the average particle diameter exceeds 5 μm, the Nb ₂ O ₅ raw material powder is coarse, so that mixing / dispersing with other raw material powders does not proceed and the second phase is present in the sintered body. Absent. The lower limit of the average particle diameter is about 0.5 μm.
Moreover, _zirconia, Y 2 _{O 3} and _{Nb 2 O 5} SiO 2 content of the feed powder is 0.03 wt% or less. If the SiO ₂ content in these raw material powders exceeds 0.03% by weight, the SiO ₂ content in the zirconia sintered body increases, resulting in a decrease in corrosion resistance and durability.

The above raw material powders are blended so as to have a predetermined composition, and are pulverized, mixed, and dispersed using water or an organic solvent by a wet pulverizer such as a known ball mill and medium stirring mill. In addition, in order to prevent wear powder from entering the grinding machine lining materials and arms, and balls filled in the grinding machine, these members and balls are made of ceramic materials with excellent wear resistance. To do. Zirconia members and balls are particularly preferable.
The average particle size of the treated powder is adjusted to 0.3 to 2.0 μm, preferably 0.3 to 1.8 μm by pulverization, mixing, and dispersion treatment. If the average particle size of the treated powder is less than 0.3 μm, the treated powder becomes very fine, and therefore the crystal particle size distribution tends to be widened. As a result, the difference between the minimum crystal particle size and the average crystal particle size widens greatly. Therefore, it is not preferable. Further, if the average particle size of the treated powder exceeds 2.0 μm, the treated powder contains a lot of coarse powder having a large particle size, so that the porosity is increased and the corrosion resistance and durability are lowered. Absent.
Control of the average particle size of the treated powder after grinding / mixing / dispersing is done by appropriately adjusting the “powder concentration”, “ball diameter and filling amount”, and “processing time” during grinding / mixing / dispersing. Do. These adjustments are matters that can be appropriately performed by those skilled in the art. In addition, the average particle diameter of the raw material powder and the treated powder in the present invention is an average value of the particle diameter of the secondary particles in which the primary particles are aggregated, and can be measured with a laser diffraction particle size distribution measuring device. .

  A compact is produced using the treated powder. When adopting a method such as press molding or rubber press molding as a molding method, a known molding aid (for example, acrylic resin, PVA, etc.) is added to the pulverized / mixed / dispersed slurry as necessary, and a spray dryer, etc. The powder for molding is prepared by drying by a known method, and the powder for molding is filled in a mold or a rubber mold and molded. In addition, when adopting the casting method, a known binder (for example, wax emulsion, acrylic resin, etc.) is added to the pulverized / mixed / dispersed slurry as required, and the waste mud is cast using a gypsum mold or a resin mold. Molding is performed by the method of filling, casting and pressure casting. Furthermore, when an extrusion molding method is employed, the obtained pulverized / mixed / dispersed slurry is dried and sized, and a binder for extrusion molding (a known binder such as carboxyl methyl cellulose or wax emulsion can be used) and water or organic Add a solvent, mix, and knead to make a forming clay. Using this molding clay, it is extruded to a predetermined shape by a known extruder.

  The molded body obtained as described above is fired at a firing temperature of 1550 to 1750 ° C. in the air. When the firing temperature is less than 1550 ° C., the average crystal grain size is less than 3 μm, which is not preferable because corrosion resistance and durability are lowered. On the other hand, if the firing temperature exceeds 1750 ° C., the average crystal grain size of the sintered body exceeds 30 μm, and the durability is lowered.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further more concretely, this invention is not limited at all by these Examples.

Examples 1-8, Comparative Examples 1-13
As a raw material powder, a zirconia raw material powder having a zirconia content of 99.8% by weight, a SiO ₂ content of 0.02% by weight and an average particle diameter of 4 μm, a Y ₂ O ₃ content of 99.9% by weight, SiO 2 ₂ content 0.01% by weight, Y ₂ O ₃ raw material powder having an average particle diameter of 4 μm, Nb ₂ O ₅ content 99.9% by weight, SiO ₂ content 0.01% by weight, average particle diameter A 1.5 μm Nb ₂ O ₅ raw material powder was used.
In Comparative Example 7, a zirconia raw material powder having a low zirconia purity having a zirconia content of 98.2% by weight, a SiO ₂ content of 0.02% by weight, and an average particle diameter of 8 μm was used.
In Comparative Example 8, a Y ₂ O ₃ raw material powder having a Y ₂ O ₃ content of 99.9% by weight, a SiO ₂ content of 0.01% by weight, and an average particle size of 9 μm and a large particle size was used.
Comparative Example 9 used Nb ₂ O ₅ raw material powder having a Nb ₂ O ₅ content of 99.9% by weight, a SiO ₂ content of 0.01% by weight, and an average particle size of 8 μm and a large particle size.
In Comparative Example 13, a zirconia raw material powder having a high zirconia content of 99.5% by weight, a SiO ₂ content of 0.07% by weight, and an average particle diameter of 5 μm and a high SiO ₂ content was used.

The Y ₂ O ₃ raw material powder and the Nb ₂ O ₅ raw material powder are blended so that the Y ₂ O ₃ content (mol%) and the Nb ₂ O ₅ / Y ₂ O ₃ molar ratio shown in Table 1 are obtained. Using water, a zirconia ball mill and balls were used for pulverization, mixing, and dispersion treatment. About the obtained processed powder, the average particle diameter was measured using the laser diffraction type particle size distribution measuring apparatus (Microtrac MT3300EX, Nikkiso Co., Ltd. product). The results are shown in Table 1. The average particle size was controlled by the processing time of pulverization / mixing / dispersion.
1% by weight of PVA binder was added to the treated slurry and dried with a spray dryer to obtain a molding powder. The obtained molding powder was press-molded using a mold at a pressure of 1 tonf / cm ² and fired in the range of 1520 to 1780 ° C. in the atmosphere to produce a plate-like sintered body. The obtained sintered body characteristics are shown in Table 1.
Examples 1 to 8 are sintered bodies within the scope of the present invention, and Comparative Examples 1 to 13 are sintered bodies that do not satisfy at least one of the requirements of the present invention.

Each sintered body was evaluated for corrosion resistance and durability as follows.
In the evaluation of corrosion resistance and durability, the reason why stress was applied with a ceramic weight is to promote the reaction with the object to be fired (PbO and PZT).
<Evaluation of corrosion resistance>
PbO (lead oxide) was adopted as the material to be fired for evaluation of corrosion resistance. A molded body formed by commercially available PbO powder (purity: 99% or more) by die press molding to have a diameter of 10 mm and a thickness of 1 mm is placed on each plate-shaped sintered body (15 mm × 15 mm × 3 mm). Further, a ceramic weight was placed on the PbO molded body, a stress of 1 kPa was applied, and the resultant was held at 870 ° C. for 20 hours. The cross section of the sintered body after the test was mirror finished, and the discolored layer thickness of the cross section was measured with an optical microscope. The results are shown in Table 1.

<Durability evaluation>
For the evaluation of durability, PZT (lead zirconate titanate), which is one of the components of the electronic component material, was employed. A molded body in which a commercially available PZT powder (purity: 99% or more) is molded to a diameter of 10 mm and a thickness of 1 mm is placed on each of the plate-like sintered bodies (15 mm × 15 mm × 3 mm), and further ceramics are placed on the PZT molded body. An operation of applying a stress of 1 kPa with a weight made of the product and holding it at 1300 ° C. for 5 hours was performed up to 20 cycles, and whether or not each plate-like sintered body was deformed, cracked or cracked was confirmed for each cycle. The results are shown in Table 1.
In addition, the numerical value in a table | surface is the number of cycles when a deformation | transformation, a crack, and a crack generate | occur | produced, and "20 <" in an Example means that a deformation | transformation, a crack, and a crack did not generate | occur | produce in 20 cycles.

Comparative Example 1 is an example of a zirconia sintered body (for example, Patent Documents 1 and 2) belonging to the prior art that does not contain Nb ₂ O ₅ .
Comparative Example 2 is an example in which the amount of cubic zirconia was less than 95% by volume because the Y ₂ O ₃ content was less than 6% by mole.
Comparative Example 3 is an example in which the second phase exists because the Y ₂ O ₃ content exceeds 12 mol%.
In Comparative Example 4, the Nb ₂ O ₅ / Y ₂ O ₃ molar ratio is less than 0.03, and thus the effect of Nb ₂ O ₅ cannot be sufficiently obtained.
Comparative Example 5 is an example in which the Nb ₂ O ₅ / Y ₂ O ₃ molar ratio exceeded 0.30, the second phase was present, and the amount of cubic zirconia was small.
Comparative Example 6 is an example in which the porosity increased because the average particle diameter of the treated powder after pulverization, mixing, and dispersion exceeded 2.0 μm.
Comparative Example 7 is an example in which the total amount of inevitable impurities in the zirconia-based sintered body is increased because low-purity zirconia raw material powder is used.
Comparative Example 8 is an example in which the monoclinic zirconia increased and the cubic zirconia decreased in the sintered body because the Y ₂ O ₃ raw material powder exceeding the average particle diameter of 5 μm was used.
Comparative Example 9 is an example in which the second phase is present in the sintered body because the Nb ₂ O ₅ raw material powder having an average particle diameter of more than 5 μm was used.
Comparative Example 10 is an example in which the average crystal grain size is small because the firing temperature is less than 1550 ° C.
Comparative Example 11 is an example in which the average crystal grain size is increased because the firing temperature exceeds 1750 ° C.
Comparative Example 12 is an example in which the ratio of the minimum crystal grain size to the average crystal grain size is small because the average particle size of the treated powder after pulverization, mixing, and dispersion is less than 0.3 μm.
Comparative Example 13 is an example in which the zirconia raw material powder having a large SiO ₂ content was used, so that the SiO ₂ content in the zirconia sintered body exceeded 0.03% by weight.

As can be seen from the evaluation results of the corrosion resistance in Table 1, the zirconia sintered bodies of the examples show excellent corrosion resistance with a discoloration layer thickness (PbO erosion depth) of 600 μm or less in the cross section, and a highly functional electronic component. It could be used as a material firing member.
On the other hand, the zirconia sintered body of the comparative example has a discoloration layer thickness exceeding 600 μm except for the comparative example 11 and is inferior in corrosion resistance, and therefore cannot be used for firing highly functional electronic component materials.
In addition, as can be seen from the durability evaluation results in Table 1, the zirconia sintered body of the example is not deformed, cracked or cracked in the plate-like sintered body even in a 20-cycle repeated test, It exhibited excellent durability and could be used for firing highly functional electronic component materials.
On the other hand, the zirconia sintered body of the comparative example is deformed, cracked and cracked before reaching 20 cycles, and is inferior in durability, so it cannot be used for firing highly functional electronic component materials. There was no.

Claims (1)

(A) Y ₂ O ₃ which is a zirconia stabilizer is contained in an amount of 6 to 12 mol% based on zirconia, and (b) the molar ratio of Nb ₂ O ₅ and Y ₂ O ₃ is 0.03 to 0.30. (C) a zirconia single phase in which the second phase does not exist as a crystal phase, (d) the zirconia crystal phase is 95% by volume or more of cubic zirconia, and (e) unavoidable The total amount of mechanical impurities is 0.3% by weight or less, the SiO ₂ content is 0.03% by weight or less, (f) the porosity is 0.5% or less, and (g) the average crystal grain size is 3 to 30 μm. (H) A firing member comprising a zirconia sintered body, wherein the ratio between the minimum crystal grain size and the average crystal grain size is 0.05 or more.