JP2004035403A - Zirconia-based powder and zirconia-based formed article - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide zirconia-based powder suitable for manufacturing a zirconia-based formed article having uniform quality and high reliability and the zirconia-based formed article obtained by using the zirconia-based powder. <P>SOLUTION: The zirconia-based powder has >0.5 μm to ≤0.8 μm mean particle diameter and in the powder, 90 vol.% of the powder has >1 μm to ≤2 μm particle diameter and the particle diameter of the 90 vol.% of the powder is 1.5-2.5 times as large as the mean particle diameter. <P>COPYRIGHT: (C)2004,JPO

Description

The present invention relates to a zirconia-based powder and a zirconia-based compact. More specifically, the present invention has a uniform quality, a zirconia-based powder suitable for producing a highly reliable zirconia-based molded body, and a uniform quality obtained using this powder, And a zirconia-based molded article having a high value

Ceramics are widely used in many fields because they have excellent electrical and magnetic properties, as well as biocompatibility, in addition to mechanical properties such as heat resistance and wear resistance. Among them, zirconia-based ceramic sheets have excellent oxygen ion conductivity, heat resistance and corrosion resistance, so they can be effectively used as sensor parts, electrolyte membranes for fuel cells, or setters for firing. Can be used.

The zirconia-based ceramic sheet is usually formed into a sheet by a doctor blade method, a calendar roll method, an extrusion method, or the like, using a slurry composed of a zirconia-based powder, an organic binder, and a solvent, and drying the solvent to remove the solvent. A green sheet is produced by volatilization, cut into a suitable size by punching, etc., then placed on a setter and baked to decompose and remove the organic binder, followed by sintering the ceramic. Have been.

数 多 く Regarding the zirconia-based powders described above, many reports have been made on the method of producing the zirconia-based powder and the physical properties of ceramics obtained by using the zirconia-based powder. However, in many cases, only the particle diameter of the raw material powder is described, and only the particle diameter and the particle diameter distribution are described at the same time in consideration of the particle diameter distribution.

For example, Patent Document 1 describes that a raw material powder having a primary particle size of 0.1 to 0.5 μm, preferably 90% by volume has a particle size distribution of 0.1 to 1 μm is used. ing.

Patent Document 2 discloses that the average particle diameter measured by the centrifugal sedimentation method is in the range of 1.3 to 3.0 μm, and the proportion of particles in the range of 1 to 20 μm is in the range of 45 to 75% by mass based on the total mass. The use of the raw material powder described in the above publication is described.

Patent Document 3 discloses (1) 87 to 90% of particles having an average particle size of 2.05 to 2.12 μm and a particle size range of 1.00 to 3.00 μm, a particle size distribution width of 0.60 to 4.00 μm, 2) 82 to 85% having an average particle size of 2.18 to 2.22 μm, a particle size range of 1.00 to 3.00 μm, a particle size distribution width of 0.80 to 4.00 μm, and (3) an average particle size of 2. It is reported that 86 to 90% of the particles having a particle size range of from 0.000 to 2.04 µm and a particle size range of from 1.00 to 3.00 µm could produce a zirconia fine powder having a particle size distribution of from 0.88 to 4.00 µm.

Patent Document 4 discloses that a ceramic sheet is manufactured using a raw material powder having an average particle diameter of 0.1 to 0.5 μm and 90% by volume or more and 1 μm or less. ing.

JP-A-1-153530 JP-A-4-130018 JP-A-4-20206 JP-A-8-151270

However, using the conventional powder having the particle size and the particle size distribution as described above, the obtained ceramic sheet has a variation in mechanical strength and the like depending on the surface portion, and has uniform quality over the entire surface. It has been difficult to produce ceramic sheets.

Thus, an object of the present invention is to provide a zirconia-based powder having uniform quality and suitable for producing a highly reliable zirconia-based compact. In particular, a zirconia-based powder having a uniform quality by a method of forming at normal pressure such as a doctor blade method or a calender roll method and sintering at normal pressure, and suitable for producing a highly reliable zirconia-based molded body. Is to provide.

Another object of the present invention is to provide a highly reliable zirconia-based compact having uniform quality and obtained by using the powder.

According to the study of the present inventors, it was found that the above object was achieved by using a zirconia-based powder having a specific particle size and a particle size distribution. The present invention has been completed based on this finding. That is, the present invention is as follows.
(1) The average particle size measured using a laser diffraction type particle size distribution analyzer is more than 0.5 μm and 0.8 μm or less, and the particle size of 90% by volume is more than 1 μm and 2 μm or less, and the particle size is 90% by volume. Is in the range of 1.5 to 2.5 times the average particle diameter.
(2) A zirconia-based compact obtained using the zirconia-based powder of (1).
(3) The zirconia-based molded article according to (2), which has a Weibull coefficient (m) value not less than 10.
(4) A zirconia-based molded article having a Weibull coefficient (m) value not less than 12.

こ と By using the zirconia-based powder of the present invention, a zirconia-based compact having uniform quality and high reliability can be obtained. In particular, when producing zirconia-based molded products by molding at normal pressure by doctor blade method, calender roll method, etc., and then sintering at normal pressure, zirconia-based molding with uniform quality and high reliability You can get the body.

ジ ル The zirconia-based molded article of the present invention has uniform quality and high reliability.

「The“ zirconia-based molded article ”of the present invention means a molded article having an arbitrary shape and a ceramic molded article obtained by firing this molded article. Representative examples of the above-mentioned shapes include two-dimensional shapes such as a sheet shape and a plate shape, three-dimensional shapes such as a spherical shape, a columnar shape, and a rectangular shape, and shapes obtained by subjecting these shapes to holes. . Further, a three-dimensional shape in which a so-called green sheet having a two-dimensional shape is further processed into a cylindrical shape, for example, is also included.

「The“ particle size ”in the present invention means the particle size of secondary particles. In general, in the case of zirconia-based powder, crystallites (primary particles) are small and aggregate by van der Waals force or the like to form secondary particles. These secondary particles are substantially crystallized by crushing or the like. Can be peptized into particles (primary particles).

ジ ル The zirconia-based powder of the present invention means a powder containing zirconia as a main component, specifically, zirconia of 60% by mass or more, preferably 80% by mass or more. Other typical components include at least one oxidation selected from yttrium (Y), cerium (Ce), calcium (Ca), magnesium (Mg), titanium (Ti), silicon (Si), and aluminum (Al). Things can be mentioned.

で も Among the zirconia-based powders, zirconia-based powders containing at least one selected from yttrium oxide, cerium oxide and calcium oxide are preferred. The content of at least one selected from yttrium oxide, cerium oxide and calcium oxide in the zirconia-based powder is preferably in the range of 1 to 20% by mass. Among them, a zirconia-based powder comprising 5 to 18% by mass of yttrium oxide and 82 to 95% by mass of zirconia is preferably used.

The zirconia-based powder of the present invention has an average particle diameter of more than 0.5 μm and 0.8 μm or less, and a particle diameter of 90% by volume of more than 1 μm and 2 μm or less, preferably an average particle diameter of more than 0.5 μm. 0.8 μm or less, 90% by volume has a particle diameter of more than 1 μm and 1.5 μm or less, more preferably 0.55 to 0.75 μm, and 90% by volume has a particle size of more than 1 μm and 1.5 μm or less. In range. The particle size of 90% by volume is 1.5 to 2.5 times, preferably 1.5 to 2 times, the average particle size.

最大 The maximum particle size of the zirconia-based powder of the present invention is 10 µm, preferably 8 µm, particularly preferably 5 µm.

Therefore, the zirconia-based powder of the present invention is characterized in that it has few coarse particles exceeding 2 µm and has a sharp particle size distribution.

The zirconia-based powder of the present invention can be prepared, for example, by finely pulverizing a zirconia-based powder having an average particle diameter of more than 0.8 μm and a 90% by volume particle diameter of more than 2 μm. A zirconia-based powder having an average particle diameter of more than 0.8 μm and a 90% by volume particle diameter of more than 2 μm can be easily obtained industrially, for example, OZC-8YC (trade name, Sumitomo Osaka Cement Co., Ltd.) And TZ-8Y (trade name, manufactured by Tosoh Corporation).

The apparatus used for the above-mentioned pulverization is not particularly limited, and the zirconia-based powder having an average particle diameter of more than 0.8 μm and a particle diameter of 90% by volume of more than 2 μm having an average particle diameter of 0.5 μm More than 0.8 μm and less than 90 μ% by volume and more than 1 μm and 2 μm or less, and 90% by volume can be pulverized to a powder having an average particle diameter of 1.5 to 2.5 times. Any of them can be used. Examples of such a crusher include a wet crusher using a ball medium. Such a wet pulverizer is commercially available, and examples thereof include Chemco Axmill V type (trade name, manufactured by Kotobuki Giken Kogyo Co., Ltd.).

For example, in the case of the Apex Mill AMV-1 type, the specifications are as follows: effective crushing chamber volume 1 liter, crushing chamber diameter 80 mm, crushing chamber height 240 mm, rotor tip peripheral speed max 6.03 m / sec (50 Hz), and rotation number 480 to 480. 1920 rpm (50 Hz). In this case, it is preferable to use a ball medium having a diameter in the range of 0.3 to 3 mm.

は In the wet grinding, the raw zirconia-based powder to be treated is mixed with a solvent to prepare a slurry, and the slurry is introduced into a grinding machine.

溶媒 As the solvent, any solvent can be used as long as it does not hinder pulverization. Representative examples include water; alcohols having 9 or less carbon atoms such as methanol, ethanol, isopropanol, butanol, and octanol; aromatic hydrocarbons such as toluene and xylene; esters such as ethyl acetate and butyl acetate; methyl cellosolve; Examples include cellosolves such as ethyl cellosolve and butyl cellosolve. These can be used alone or in combination of two or more. Typical examples of the mixed solvent include a mixture of a water-insoluble solvent and a water-soluble solvent such as toluene / ethanol, ethyl acetate / isopropanol, and toluene / butyl cellosolve.

The concentration of the raw material zirconia-based powder in the slurry is usually 30 to 70% by mass, and preferably 30 to 50% by mass. If the concentration is too high, the pulverizing operation becomes difficult. In order to improve the dispersion of the raw zirconia powder, a dispersant can be added. By using a dispersant, fine pulverization can be performed efficiently even when the concentration of the raw material zirconia-based powder in the slurry is set to a high range of 40 to 70% by mass, particularly 45 to 55% by mass. Thereby, productivity can be further increased.

Examples of the dispersant include organic acids such as formic acid, citric acid and tartaric acid; polyelectrolytes such as polyacrylic acid and ammonium polyacrylate; multi-chain high molecular weight nonionic surfactants, carboxylic acid type surfactants, β Surfactants such as naphthalenesulfonic acid ammonium salt, polymeric surfactant, and nonionic surfactant (for example, Discols (trade name) manufactured by Daiichi Kogyo Seiyaku Co., Ltd., homogenols (trade name) Kao ( Ethers such as polyoxyethylene nonyl phenyl ether and polyoxyethylene alkyl ether (for example, ionettes (trade name) manufactured by Sanyo Chemical Industries, Ltd.); partial esters of dicarboxylic acids or carboxylic acids Copolymers of partial esters (for example, Bunsan G-200 (trade name) manufactured by Kyoeisha Chemical Co., Ltd., Floren G-700) (Trade name) manufactured by Kyoeisha Chemical Co., Ltd.); dispersants such as acrylic acid ester and maleate ester (Oricox (trade name) manufactured by Kyoeisha Chemical Co., Ltd.); glycerin, sorbitan fatty acid ester, polyoxyethylene fatty acid Diesters and the like can be mentioned.

Among them, a copolymer of a partial ester of dicarboxylic acid or a partial ester of carboxylic acid with a surfactant having an acid value is particularly preferably used.

添加 The amount of the dispersant added is 0.01 to 5% by mass, preferably 0.3 to 2% by mass of the raw material zirconia-based powder.

Therefore, the raw material zirconia-based powder is dispersed in a solvent in the presence of a dispersant to prepare a slurry in which the concentration of the raw material zirconia-based powder in the slurry is 40 to 70% by mass. It is preferable to provide for wet grinding.

The slurry may be prepared by introducing a raw material zirconia-based powder, a solvent, and a dispersant into a pulverizer, or may be prepared by previously mixing them to prepare a slurry and then introducing the slurry. The wet pulverization may be a batch type or a continuous type.

The average particle diameter obtained as described above is more than 0.5 μm and 0.8 μm or less, the 90% by volume particle diameter is more than 1 μm and 2 μm or less, and the 90% by volume particle diameter is 1.5 to 1.5 μm of the average particle diameter. The slurry containing 2.5 times the zirconia-based powder may be subjected to operations such as drying under reduced pressure to obtain a zirconia-based powder, or may be used as it is, or may be formed into a green body after adding a predetermined amount of a necessary binder and plasticizer. .

ロ ー タ リ ー A rotary evaporator, a vibration fluidized dryer (for example, VU-60 (trade name) manufactured by Chuo Koki Co., Ltd.) or the like can be used for the operation such as the drying under reduced pressure.

平均 The average particle diameter and the particle diameter of 90% by volume of the zirconia-based powder obtained by the above wet pulverization were measured using a laser diffraction particle size distribution analyzer SALD-1100 manufactured by Shimadzu Corporation.

ジ ル The zirconia-based compact of the present invention can be prepared according to a conventional method except that the zirconia-based powder of the present invention is used as the powder. Hereinafter, a green sheet as a representative example of the zirconia-based molded article of the present invention will be described as an example.

A binder and a solvent are further added to the zirconia-based powder of the present invention, and if necessary, a dispersant, a plasticizer, and the like are blended, and the mixture is slurried by means such as a normal ball mill method. It is formed into a sheet by a method such as a green sheet.

The binder is not particularly limited, and may be appropriately selected from commonly used organic or inorganic binders. Examples of organic binders include ethylene copolymers, styrene copolymers, acrylate and methacrylate copolymers, vinyl acetate copolymers, maleic acid copolymers, vinyl butyral resins, vinyl acetal resins, and vinyl Examples include formal resins, vinyl alcohol resins, waxes, and celluloses such as ethyl cellulose. Examples of the inorganic binder include zirconia sol, silica sol, alumina sol, titania sol, and the like.

(4) The amount of the binder used can be appropriately determined in consideration of the viscosity of the slurry and the like in addition to the strength and flexibility of the green sheet. For example, it is used in a ratio of 10 to 30 parts by mass with respect to 100 parts by mass of the zirconia-based powder of the present invention.

The solvent is not particularly limited and may be appropriately selected from commonly used water and organic solvents. Representative examples of the organic solvent include alcohols such as methanol, ethanol, 2-propanol, 1-butanol and 1-hexanol; ketones such as acetone and 2-butanol; and aliphatic hydrocarbons such as pentane, hexane and heptane. Aromatic hydrocarbons such as benzene, toluene, xylene and ethylbenzene; and acetates such as methyl acetate, ethyl acetate and butyl acetate.

The amount of the solvent used can be appropriately determined in relation to the viscosity of the slurry. For example, the slurry may be used in such a ratio that the viscosity of the slurry becomes 20 to 200 poise.
The slurry thus obtained is cast on a polymer film such as polyethylene terephthalate (PET) by a usual coating method such as a doctor blade method or a calendar roll method, and then dried to form a green sheet. The thickness of this green sheet is usually 0.1 to 2 mm.

The green sheet thus obtained is placed on a general-purpose sintering plate, for example, a porous alumina plate, and sintered at normal pressure at a temperature of 1200 to 1700 ° C. to obtain a zirconia ceramic sheet. .

The zirconia-based powder of the present invention can be molded by various molding methods such as injection molding, press molding, casting molding, extrusion molding, sheet molding, etc., by the doctor blade method, calender roll method, etc. It is particularly preferably used when producing a zirconia-based molded body by molding under normal pressure, and further by sintering this at normal pressure to produce a zirconia-based ceramic molded body. That is, by using the zirconia-based powder of the present invention when manufacturing a zirconia-based molded article by such a method, a zirconia-based molded article having uniform quality and high reliability can be produced.

ワ イ In the zirconia-based molded article of the present invention, in particular, with regard to the zirconia-based ceramic molded article, generally, the Weibull coefficient (m) value is used as a measure for indicating the uniformity of quality and, consequently, the reliability. This is a statistical representation of variations in mechanical strength and the like. The higher the Weibull coefficient (m), the smaller the variation in mechanical strength, which is practically preferable. According to the present invention, a zirconia-based molded body having a Weibull coefficient (m) value higher than 10 can be obtained.

Hereinafter, the present invention will be described more specifically with reference to examples.
Example 1
Apex Mill AM- with 4 kg of commercially available zirconia-based powder OZC-8YC (trade name, manufactured by Sumitomo Osaka Cement Co., Ltd.) having an average particle diameter of 0.84 μm and a particle diameter of 90% by volume of 2.65 μm together with 6 kg of pure water. 1 (trade name, manufactured by Kotobuki Giken Kogyo Co., Ltd., mill crushing chamber diameter: 8 cm) and crushed under the following conditions.
Ball media: 0.5 mm diameter zirconia ball (4 kg)
Rotor tip peripheral speed: 7m / sec (set by adjusting mill motor power)
Pulverization time: 1 hour The slurry obtained by the wet pulverization was put into a 10-liter rotary evaporator, an equal amount of octanol was further added, and water was distilled under heating and reduced pressure to obtain an octanol-substituted slurry. The slurry was further heated and reduced in pressure to distill octanol, and then dried under reduced pressure to obtain pulverized fine powder (A).

When this powder (A) was measured using a particle size distribution analyzer SALD-1100 manufactured by Shimadzu Corporation, the average particle diameter was 0.66 μm, and the particle diameter of 90% by volume was 1.3 μm. Further, the maximum particle size was 3.7 μm.
Example 2
5.5 kg of commercially available zirconia-based powder OZC-8YC (trade name, manufactured by Sumitomo Osaka Cement Co., Ltd.) having an average particle diameter of 0.84 μm and a particle diameter of 90% by volume of 2.65 μm, and 44 g of formic acid as a dispersing agent. 4.544 kg of the pure water added was put into Apex Mill AM-1 (trade name, manufactured by Kotobuki Giken Kogyo Co., Ltd., mill crushing chamber diameter: 8 cm) and crushed under the following conditions.
Ball media: 0.5 mm diameter zirconia ball (4 kg)
Rotor tip peripheral speed: 5m / sec (set by adjusting mill motor power)
Pulverization time: 10 minutes Hereinafter, a pulverized fine powder (B) was obtained in the same manner as in Example 1, and the average particle diameter and the particle diameter of 90% by volume were measured. The average particle diameter of the powder (B) was 0.6 μm, and the particle diameter of 90% by volume was 1.12 μm. Further, the maximum particle size was 3.7 μm.
Example 3
50 parts by mass of toluene / ethyl acetate (1/1 mass ratio) obtained by dissolving 15 parts by mass of a methacrylic acid copolymer in 100 parts by mass of the zirconia-based powders (A) and (B) prepared in Examples 1 and 3 respectively. After adding 2 parts by weight of dibutyl phthalate as a plasticizer and mixing with a ball mill to adjust the viscosity, a green sheet having a thickness of 0.25 mm was produced by a doctor blade method.

The green sheet was fired at 1450 ° C. for 2 hours to obtain a zirconia ceramic sheet having a thickness of 0.2 mm. The Weibull coefficient (m) value of this sheet was determined by the following method. Table 1 shows the results.
<Weibull coefficient (m) value>
Twenty sheet-shaped test pieces of 4 mm (width) x 0.2 mm (thickness) x 40 mm (length) were produced. For these test pieces, the three-point bending strength was measured according to the method of JIS R1601, without adjusting the surface roughness or chamfering.

Next, "Refractory" 39-489, 1987-No. No. 9 Yoshiharu Ozaki “Estimation of Strength and Reliability of Ceramics” Equation (2) described in the right column of page 11

(Where Pf is the probability of fracture, defined by Pf = n / (N + 1) (where N is the number of samples and n is the nth sample), σf is the bending bending strength, and m is Weibull Σ0 is a normalization factor, and σu is a stress value that becomes 0 below this breaking bending strength), σf is a measured value of the above three-point bending strength, and the vertical axis is InIn ｛1 / (1 −Pf)｝ and In (σf−σu) on the horizontal axis, a graph was drawn. Note that -mIn? 0 is an intercept of the graph. From this slope, m was obtained by the least square method.
Example 4
After putting the zirconia-based powders (A) and (B) prepared in Example 1 and Example 2 in a rubber bag, respectively, they were subjected to hydrostatic pressure press at 2000 kg / cm ² for 10 minutes to obtain a bulk of 30 mm × 6 mm × 100 mm. Got a body. Next, this bulk body was cut into 4 mm × 4 mm × 40 mm, the surface was polished, and then fired at 1500 ° C. for 2 hours to obtain a zirconia-based test piece.

Using this test piece, the Weibull coefficient (m) value was determined in the same manner as in Example 3. Table 2 shows the results.
Comparative Example 1
In Example 3, in place of the zirconia-based molded product (A) prepared in Example 1, a commercially available zirconia-based material having a mean particle diameter of 0.84 μm and 90% by volume having a particle diameter of 2.65 μm as the raw material powder was used. A zirconia ceramic sheet was prepared in the same manner as in Example 3 except that the powder was used, and the Weibull coefficient (m) value was obtained. The results are shown in Table 1.
Comparative Example 2
In Example 4, in place of the zirconia-based powder (A) prepared in Example 1, a commercially available zirconia-based powder having a mean particle diameter of 0.84 μm and 90% by volume of 2.65 μm as the raw material powder was used. A zirconia-based bulk body was prepared in the same manner as in Example 4 except that the powder was used, and the Weibull coefficient (m) value was obtained. The results are shown in Table 2.

か ら From the results of Tables 1 and 2, it can be seen that the zirconia-based molded article of the present invention has a high Weibull coefficient, uniform quality, and high reliability.

Industrial applications

Since the zirconia-based molded article of the present invention has excellent oxygen ion conductivity, heat resistance, and corrosion resistance, it can be effectively used as a sensor component, an electrolyte membrane for a fuel cell, or a firing setter. Can be.

Claims (4)

The average particle diameter measured using a laser diffraction type particle size distribution analyzer is more than 0.5 μm and less than 0.8 μm, the particle diameter of 90% by volume is more than 1 μm and less than 2 μm, and the particle diameter of 90% by volume is an average particle. A zirconia-based powder having a diameter of 1.5 to 2.5 times. A zirconia-based compact obtained by using the zirconia-based powder according to claim 1. The zirconia-based molded article according to claim 2, having a Weibull coefficient (m) value not less than 10. A zirconia-based molded article having a Weibull coefficient (m) value not less than 12.