JP2008024555A - Zirconia fine powder, its manufacturing method and its use - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a zirconia fine powder having excellent moldability, low temperature-sinterability, and quality-reliability as a sintered compact, and powder granules using the same. <P>SOLUTION: The zirconia fine powder contains one or more kinds selected from yttria, calcia, magnesia, and ceria as a stabilizer and has a BET specific surface area of 6-10 m<SP>2</SP>/g, an average particle diameter of 0.4-0.6 μm, and ratios of particles having particle diameters of 0.2 μm, 1 μm, and 2 μm in the cumulative curve of its particle size distribution are 0%, not less than 95%, and 100%, respectively. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a novel zirconia fine powder which is used as a raw material for structural ceramics such as optical connector parts, precision processed parts and pulverizer members, and which has particularly good formability and excellent low-temperature sinterability, and a method for producing the same. The present invention relates to zirconia granules obtained by making the zirconia fine powder into a slurry and spray granulating.

  Since zirconia ceramics exhibit high strength and high toughness, they are used in a wide range of applications such as optical connector parts, precision processed parts, grinding media, pulverizer parts, blades and the like. However, when such zirconia ceramics having high strength and high toughness are exposed to a temperature of 200 to 300 ° C. for a long time in air, the tetragonal crystal, which is a metastable phase, is converted to a monoclinic crystal having a stable phase by about 4%. It has been pointed out that microcracks are generated and the strength and toughness are lowered, that is, deteriorated. In order to improve this defect, the sinterability of the zirconia powder as a starting material is improved to improve the deterioration resistance of the zirconia ceramics. In order to improve the sinterability, it is effective to increase the specific surface area of the zirconia powder, but on the other hand, as the specific surface area increases, the cohesiveness of the powder increases and it becomes difficult to form. . Normally, when dry pressing is performed using highly agglomerated powder, the density of the compact becomes uneven and lamination occurs, and the adhesion between the mold wall surface and the compact is large during pressing, and molding is performed from the mold. When the body is taken out, scratches and cracks occur in the sintered body that is obtained when the fragments of the molded body easily stick to the mold. Such scratches and cracks are more likely to occur as the specific surface area increases.

For example, zirconium oxide powder having a BET specific surface area of 1 to 10 m ² / g, an average particle diameter of 0.1 to 1 μm, and a proportion of particles having a cumulative distribution of 0.1 μm or less and more than 10 μm is 5% or less has been proposed. (Patent Document 1). Although this zirconium oxide powder exhibits good moldability due to its low specific surface area, the sintering temperature is as high as 1500 ° C., and there is still room for improvement in terms of sinterability.

Recently, zirconia powder with good sinterability has been proposed (for example, Patent Document 2). This zirconia powder has ^two peaks in a BET specific surface area of 5 to ²⁰ m ² / g, an average particle size of 0.2 to 1 μm, and a particle size distribution of 0.1 to 10 μm. It is disclosed that a high-density zirconia sintered body can be obtained at a temperature of 1350 ° C. when a small amount of alumina is contained in and then molded and sintered. However, the powder of Patent Document 2 has an average particle size of 0.7 μm and contains many particles of 2 μm or more.

  Recently, there has been an increasing demand for higher performance in various applications. In particular, a highly reliable zirconia ceramic that does not deteriorate even under severe conditions of use is desired, and has good formability and is fired at a low temperature. There is a need for zirconia powders to set.

JP-A-4-357115 (Claim 1, Example 1) JP-A-2004-182554 (Claim 1, Example 4)

  In the present invention, the disadvantages in the conventional method as described above are eliminated, the moldability is good, and the low-temperature sinterability is excellent. In addition to these, the quality of the sintered body is also excellent in reliability. An object of the present invention is to provide a zirconia fine powder and a method capable of producing the zirconia fine powder by a simple process.

  The present inventors have studied in detail the relationship between the particle size distribution of zirconia powder and the molding and sintering properties, and have reached the present invention.

That is, the present invention
1) A zirconia fine powder containing at least one of yttria, calcia, magnesia and ceria as a stabilizer, the zirconia fine powder having a BET specific surface area of 5 to 10 m ² / g and an average particle size of 0.3 to Zirconia fine powder in the range of 0.6 μm, and in the cumulative curve of the particle size distribution, the proportions of particles having a particle size of 0.2 μm, 1 μm and 2 μm are 0%, 95% or more and 100%, respectively. .
2) The zirconia fine powder according to 2) above, wherein the peak of the particle size distribution exists only in the range of 0.2 to 2 μm.
3) The fine zirconia powder of the above 1) and 2) containing 2 to 4 mol% of yttria as a stabilizer and having a monoclinic phase ratio of 10 to 40%.
4) The zirconia fine powder according to 1) to 3) above, wherein the zirconia fine powder contains one or more additives.
5) The zirconia fine powder according to 4) above, wherein the cation of the additive is a cation having an ionic radius smaller than that of zirconium ions and / or a cation having a valence other than tetravalent.
6) The fine zirconia powder according to the above 4) and 5), wherein the cation of the additive is at least one cation selected from the group consisting of aluminum, silicon and germanium.
7) In a method of obtaining a zirconia powder by drying, calcining, and pulverizing a hydrated zirconia sol obtained by hydrolysis of an aqueous zirconium salt solution, an alkali metal hydroxide and / or an alkaline earth metal water is added to the aqueous zirconium salt solution. Add one or more compounds of yttrium, calcium, magnesium and cerium as raw materials for the stabilizer to the hydrated zirconia sol obtained by hydrolysis until the reaction rate reaches 98% or more after adding the oxide And dried and calcined in the range of 1000 to 1200 ° C. to obtain zirconia powder, and then the zirconia balls having a diameter of 3 mm or less so that the average particle diameter of the zirconia powder is in the range of 0.3 to 0.6 μm. The method for producing a zirconia fine powder according to any one of 1) to 3) above, wherein the pulverization is performed by wet pulverization using a zirconia.
8) In the method for producing zirconia fine powder according to 7), an additive is added to the hydrated zirconia sol or the powder obtained by calcining. Production method.
9) The method for producing a fine zirconia powder according to 7) and 8) above, wherein the yttrium compound is added in an amount of 2 to 4 mol% in terms of oxide.
10) Obtained by spray granulating the zirconia fine powder described in 1) to 6) above, having an average particle size of 30 to 80 μm and a light bulk density of 1.00 to 1.40 g / cm ³ . Zirconia granules.

“A zirconia fine powder containing at least one of yttria, calcia, magnesia and ceria as a stabilizer, the zirconia fine powder has a BET specific surface area of 5 to 10 m ² / g and an average particle size of 0.1 of the present invention. Zirconia is in the range of 3 to 0.6 μm, and the proportion of particles having a particle size of 0.2 μm, 1 μm, and 2 μm in the cumulative particle size distribution curve is 0%, 95% or more, and 100%, respectively. When the “fine powder” is molded and sintered, a zirconia sintered body having a high sintering density and bending strength can be obtained at a low sintering temperature, and the present invention has been completed.

  Hereinafter, the present invention will be described in more detail.

  In the present specification, the “average particle size” related to the fine zirconia powder is a median value (median diameter; particle size corresponding to 50% of the cumulative curve) of the cumulative particle size distribution expressed by volume. The diameter of a sphere having the same volume as the particle, which can be measured by a particle size distribution measuring apparatus using a laser diffraction method.

“Stabilizer concentration” refers to a value expressed as mole% of the ratio of stabilizer / (ZrO ₂ + stabilizer).

The “monoclinic phase ratio (f _m )” means the (111) and (11-1) planes of the monoclinic phase, the (111) plane of the tetragonal phase, and the cubic crystal by powder X-ray diffraction (XRD) measurement. The diffraction intensities of the (111) plane are calculated, and the values calculated by the following formula 1 are used.

ここで、Ｉは各回折線のピーク強度，添字ｍ，ｔ及びｃは、それぞれ単斜晶相，正方晶相，立方晶相を表す。

Here, I represents the peak intensity of each diffraction line, and subscripts m, t, and c represent a monoclinic phase, a tetragonal phase, and a cubic phase, respectively.

  The “ion radius” refers to a value reported by Shannon (Acta. Crystallogr., A32, 751-67 (1976).).

“Additive content” refers to a value expressed as a weight% ratio of additive / (ZrO ₂ + stabilizer + additive). Here, the additive is a value converted to an oxide.

  The “reaction rate” related to the hydrated zirconia sol is obtained by ultrafiltration of a hydrated zirconia sol-containing liquid and determining the amount of zirconium in the unreacted substance present in the filtrate by inductively coupled plasma emission spectrometry. The amount of zirconia sol produced is calculated and the value expressed as the ratio of the amount of hydrated zirconia sol to the amount of raw material charged.

  The “average particle diameter” is measured with a particle size distribution measuring apparatus or an electron microscope, and refers to a value obtained by, for example, a photon correlation method.

  The zirconia fine powder of the present invention must contain at least one of yttria, calcia, magnesia and ceria as a stabilizer. When molding and sintering zirconia fine powder that does not contain the above stabilizers, expansion and contraction associated with martensite transformation occurs during sintering, and as a result, the material is destroyed. Because it becomes.

The fine zirconia powder must have a BET specific surface area in the range of 5 to 10 m ² / g. When the BET specific surface area of the zirconia fine powder is smaller than 5 m ² / g, it becomes a powder that is difficult to sinter on the low temperature side, and when larger than 10 m ² / g, the cohesive force between particles becomes a remarkable powder, As ceramic raw material powder, it is difficult to handle and unsuitable. A more preferable BET specific surface area is 6 to 9 m ² / g.

  The fine zirconia powder of the present invention needs to have an average particle size in the range of 0.3 to 0.6 μm. If the average particle size of the zirconia fine powder is smaller than 0.3 μm, the number of fine particles that increase the cohesiveness of the powder increases, making it difficult to mold. On the other hand, if the average particle size is larger than 0.6 μm, coarse particles containing hard agglomerated particles are formed. This is because the amount increases, so that it becomes difficult to mold, and the coarse particles inhibit the densification of the sintering, so that the sinterability becomes poor. A preferable average particle diameter is 0.4 to 0.5 μm.

  Furthermore, in the cumulative curve of the particle size distribution, the proportion of particles having a particle size of 0.2 μm, 1 μm and 2 μm should be 0%, 95% or more and 100%, respectively. When the proportion of particles with a particle size of 0.2 μm is greater than 0%, the number of fine particles that increase the cohesiveness of the powder increases, whereas the proportion of particles with a particle size of 1 μm is less than 95%, or This is because when the proportion of particles having a particle size of 2 μm is less than 100%, coarse particles containing hard aggregated particles increase, and as described above, the moldability and sinterability are poor. If the proportion of particles with a particle size of 1 μm is 100%, the sinterability is further improved.

  In addition to the above conditions, if the peak of the particle size distribution exists only in the range of 0.2 to 2 μm, the moldability and sinterability will be even better.

  Since the characteristics of zirconia ceramics vary depending on the type and concentration of the stabilizer, the stabilizer may be selected as necessary and the concentration of the stabilizer may be set. If the stabilizer is a solid solution in the zirconia particles, the densification of sintering proceeds uniformly, which is more preferable. In particular, as long as it contains 2 to 4 mol% of yttria as a stabilizer and has a crystal structure with a monoclinic phase ratio of 10 to 40%, a sintered body obtained by molding and sintering is used. The size of the remaining pores is reduced and the number thereof is reduced, so that the sintered body becomes a high-density sintered body and becomes zirconia ceramics excellent in mechanical strength and toughness. A more preferable yttria concentration is 2.3 to 3.5 mol%, and a monoclinic phase rate is 10 to 30%.

  Furthermore, when the above zirconia fine powder contains one or more additives, the densification rate at the time of molding and sintering is accelerated, so that the sinterability is further improved. When such a zirconia fine powder is used as a raw material and then molded and sintered, a high-density sintered body can be obtained at a low sintering temperature. High zirconia ceramics. In particular, if the cation of the additive has an ionic radius (r) smaller than the ionic radius of zirconium ion (0.86 angstrom) and / or the valence (Z) is other than tetravalent, This is more preferable because the densification speed of the knot is significantly accelerated. The optimum additive content is 0.05 to 1% by weight in terms of oxide. Additive cations include aluminum (r = 0.68 angstrom, Z = 3), silicon (r = 0.54 angstrom, Z = 4) and germanium (r = 0.67 angstrom, Z = 4). One or more selected from the group is effective, and among these, the combination of aluminum and germanium is the best.

  In obtaining the zirconia fine powder of the present invention, the hydrated zirconia sol obtained by hydrolysis of the zirconium salt aqueous solution is dried, calcined, and pulverized to obtain the zirconia powder. To the hydrated zirconia sol obtained by performing hydrolysis until the reaction rate is 98% or more after adding the product and / or alkaline earth metal hydroxide, and yttrium, calcium, magnesium and It is necessary to add and dry one or more cerium compounds. If the alkali metal hydroxide and / or alkaline earth metal hydroxide is not added to the zirconium salt aqueous solution, or if the rate of formation of the hydrated zirconia sol is less than 98%, it is generated by the addition of the hydroxide. Precipitation of hydrated zirconia sol with a very small particle diameter, or strong sintering between particles due to unreacted substances occurs, so that coarse particles containing remarkably agglomerated particles and containing hard agglomerated particles This is because, as described above, it is difficult to mold and the sinterability is poor. The addition amount of the preferred alkali metal hydroxide and / or alkaline earth metal hydroxide is in the range of 0.005 to 0.1 as the molar concentration ratio of [OH] / [Zr], and the preferred reaction rate is 99%. That's it. There is no restriction on the method of mixing the hydrated zirconia sol and the raw material of the stabilizer. For example, a predetermined amount of the raw material of the stabilizer may be added to the hydrous hydrated zirconia sol-containing liquid, or hydrolysis may be performed. It may be added in advance to the previous aqueous zirconium salt solution. Examples of the compound used as the raw material for the stabilizer include chloride, fluoride, nitrate, carbonate, sulfate, acetate, oxide, hydroxide and the like. When 2-4 mol% of yttrium compound is added in terms of oxide as a raw material for the stabilizer, the monoclinic phase ratio of the zirconia fine powder obtained under the above calcining and pulverization conditions is in the range of 10-40%, As described above, the mechanical strength and toughness are excellent. A more preferred yttria concentration is 2.3 to 3.5 mol%. As for the method of drying the hydrated zirconia sol, for example, the mixed solution is used as it is or spray-dried by adding an organic solvent to the mixed solution, and after adding alkali or the like to the mixed solution and filtering and washing with water. The method of drying can be mentioned.

  The above hydrated zirconia sol is obtained by adding an alkali metal hydroxide and / or an alkaline earth metal hydroxide to a zirconium salt aqueous solution and hydrolyzing it, so that a reaction rate of 98% or more is obtained. As long as it is a method, it may be obtained under any reaction conditions. For example, a predetermined amount of an alkali metal hydroxide and / or alkaline earth metal hydroxide is added to a zirconium salt aqueous solution to cause hydrolysis, and a hydrated zirconia sol obtained by hydrolysis and an alkali metal hydroxide and / or Examples thereof include a method in which a predetermined amount of an alkaline earth metal hydroxide is added to a zirconium salt aqueous solution to cause hydrolysis. In particular, a part of the hydrated zirconia sol-containing liquid obtained by hydrolysis of an aqueous zirconium salt solution to which a predetermined amount of alkali metal hydroxide and / or alkaline earth metal hydroxide is added is continuously and / or removed from the reaction vessel. Discharge intermittently and keep the volume of the hydrated zirconia sol-containing liquid constant so that a predetermined amount of alkali metal hydroxide and / or alkaline earth metal hydroxide equivalent to the discharge amount is maintained. It is effective to hydrolyze the aqueous zirconium salt solution to which the product is added while continuously and / or intermittently supplying it to the reaction vessel, since a hydrated zirconia sol having a higher reaction rate can be obtained efficiently.

  Zirconium salts used for the production of the hydrated zirconia sol include zirconium oxychloride, zirconyl nitrate, zirconium chloride, zirconium sulfate and the like, but in addition, a mixture of zirconium hydroxide and acid may be used. Examples of the alkali metal hydroxide and / or alkaline earth metal hydroxide added to the zirconium salt aqueous solution include hydroxides such as lithium, sodium, potassium, magnesium, and calcium. The hydroxide is preferably added as an aqueous solution.

  Next, in the present invention, the dried powder of the hydrated zirconia sol obtained above is calcined at a temperature of 1000 to 1200 ° C. If the calcination temperature is outside this range, the agglomeration property of the zirconia fine powder obtained under the following pulverization conditions of the present invention becomes remarkably strong or the average particle size becomes 0. The proportion of particles with a particle size of 0.2 μm, 1 μm or 2 μm outside the range of 3 to 0.5 μm and in the cumulative curve of particle size distribution is greater than 0%, less than 95% or less than 100%, respectively. The zirconia fine powder of the present invention is not easily obtained. A more preferable calcining temperature is 1000 to 1100 ° C. The holding time of the calcining temperature is preferably 0.5 to 10 hours, and the temperature raising rate is preferably 0.5 to 10 ° C./min. If the holding time is shorter than 0.5, uniform calcination is difficult, and if it is longer than 10 hours, the productivity is lowered, which is not preferable. Also, when the rate of temperature rise is less than 0.5 ° C / min, the time until the set temperature is reached is lengthened. Sex is reduced.

  Next, it is preferable to wet pulverize the calcined powder obtained above using zirconia balls having a diameter of 3 mm or less until the average particle diameter is in the range of 0.3 to 0.6 μm.

  If an alkali metal and / or alkaline earth metal hydroxide is not added to the zirconium salt aqueous solution during the synthesis of the hydrated zirconia sol, this wet pulverization cannot be carried out efficiently. Although this cause is not certain, it is considered that the cohesive strength between the zirconia powders is reduced by adding the hydroxide.

  When wet pulverization is performed using zirconia balls having a diameter larger than 3 mm, the average particle size is larger than 0.6 μm, and the proportion of the particles is 95% in the cumulative particle size distribution curve of 1 μm and 2 μm, respectively. It becomes difficult to obtain the zirconia fine powder of the present invention. A more preferable diameter of the zirconia ball is 2 mm or less. As a grinding device, a vibration mill or a continuous medium stirring mill may be used. The grinding conditions vary depending on the model, but in the case of a vibration mill, the slurry concentration is 30 to 60 wt% and 5 to 30 hours is good. In the case of a medium stirring mill, the slurry concentration is 30 to 60 wt% and 10 to 30 hours is optimal. is there. Washing the calcined powder with water or dilute ammonia water before pulverization removes a small amount of impurities that hinder sintering, which is derived from the zirconium salt raw material, thus improving the sinterability. Is effective.

  If necessary, when obtaining a zirconia fine powder containing an additive, the additive may be added to the hydrated zirconia sol, or the additive may be added to the calcined powder and wet pulverized. Examples of the raw material compound in which the cation of the additive is aluminum include alumina, hydrated alumina, alumina sol, aluminum hydroxide, aluminum chloride, aluminum nitrate, and aluminum sulfate. Examples of the raw material compound whose cation is silicon include silica, silica sol, and silicic acid. Examples of the raw material compound whose cation is germanium include germanium oxide and germanium hydroxide.

The zirconia fine powder obtained in the present invention is made into a slurry and spray-dried to obtain zirconia granules having a particle size of 30 to 80 μm and a light bulk density of 1.10 to 1.40 g / cm ³ . Although it does not specifically limit about the manufacturing method of a granule, For example, it is possible to manufacture a zirconia granule from the zirconia fine powder obtained by this invention by the method of Unexamined-Japanese-Patent No. 10-194743.

The zirconia fine powder of the present invention is a powder in which there are no fine particles of less than 0.2 μm, the ratio of coarse particles of 1 μm or more is reduced, and the main particle size distribution is controlled to 1 μm or less. Compared with this, the moldability and low-temperature sinterability are remarkably improved, and the quality of the sintered body is excellent in reliability.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to these Examples at all.

  In the examples, the average particle size of the hydrated zirconia sol was determined by a particle size distribution measuring apparatus using a photon correlation method. The average particle diameter of the zirconia fine powder was measured using a Microtrac particle size distribution meter (manufactured by Honeywell, 9320-HRA). As pretreatment conditions for the sample, the powder was suspended in distilled water and dispersed using an ultrasonic homogenizer (manufactured by Nippon Seiki Seisakusho, US-150T) for 3 minutes. The monoclinic phase ratio determined by XRD measurement was calculated from Equation 1 (in all examples, cubic crystals were not included). Moreover, the average particle diameter of the zirconia granule was calculated | required with the screening test method.

The raw material powder was molded by a mold press at a molding pressure of 700 kgf / cm ² , and the obtained molded body was sintered at a predetermined temperature (holding time 2 hours). The relative density of the obtained sintered body was measured by Archimedes method, and the theoretical density was calculated as 6.08 g / cm ³ . The strength of the sintered body was evaluated by a three-point bending measurement method. The deterioration test was evaluated by immersing the sintered body in 140 ° C. hot water for 5 hours and determining the ratio of the monoclinic phase to be formed (monoclinic phase ratio). The monoclinic phase rate was obtained by Equation 1 using the same calculation method as that of the monoclinic phase rate of the zirconia fine powder by performing XRD measurement on the sintered body subjected to the immersion treatment.

Example 1
A potassium hydroxide aqueous solution was added to a 0.4 mol / liter zirconium oxychloride aqueous solution to prepare an aqueous solution having a molar concentration ratio of [OH] / [Zr] = 0.02. While stirring this solution in a flask equipped with a reflux condenser, the hydrolysis reaction was carried out at the boiling temperature for 350 hours. The reaction rate of the obtained hydrated zirconia sol was 99%. To this hydrated zirconia sol, yttrium chloride was added to a yttria concentration of 3 mol%, dried, and calcined at a temperature of 1100 ° C. for 2 hours. After the obtained calcined powder was washed with water, alumina powder was added so that the alumina content was 0.25 wt%, and distilled water was further added to make a slurry having a zirconia concentration of 45 wt%. This slurry was pulverized with a vibration mill for 8 hours using zirconia balls having a diameter of 2 mm and dried. Table 1 shows values of the BET specific surface area, average particle diameter, particle diameter of 0.2 μm, 1 μm and 2 μm, and monoclinic phase ratio of the obtained zirconia fine powder.

  Subsequently, the zirconia fine powder obtained above was press-molded and sintered under the condition of 1350 ° C. Table 2 shows the relative density, bending strength, and monoclinic phase rate after the deterioration test of the obtained sintered body. The monoclinic phase rate after the deterioration test was 0%, and it was confirmed that the sintered body was extremely difficult to deteriorate. Further, when an impregnation test with a red dye was performed, scratches and cracks due to lamination or the like were not observed on the surface of the sintered body.

Example 2
Distilled water was added to the hydrated zirconia sol of Example 1 to prepare a solution having a zirconia equivalent concentration of 0.3 mol / liter. Using this as a starting solution, 5% by volume of the solution is intermittently discharged from the reaction vessel, and 0.3 mol / liter of the same amount as the discharged amount so that the volume of the solution is kept constant. Hydrolysis reaction was carried out at boiling temperature for 200 hours while supplying an aqueous zirconium oxychloride solution ([OH] / [Zr] = 0.02) to which a sodium hydroxide aqueous solution was added to the reaction vessel every 30 minutes. The reaction rate of the hydrated zirconia sol discharged from the reaction vessel was 99%. To this hydrated zirconia sol, yttrium chloride was added to a yttria concentration of 3 mol%, dried, and calcined at a temperature of 1090 ° C. for 2 hours. The obtained calcined powder was washed with water, and distilled water was added to make a slurry having a zirconia concentration of 45% by weight. This slurry was pulverized for 24 hours with a vibration mill using zirconia balls having a diameter of 2 mm and dried. The characteristics of the obtained zirconia fine powder are shown in Table 1. The particle size distribution (frequency and cumulative curve) of the zirconia fine powder is shown in FIG.

  Subsequently, the zirconia fine powder obtained above was press-molded and sintered under the condition of 1400 ° C. Table 2 shows the characteristics of the obtained sintered body. When an impregnation test with a red dye was performed, scratches and cracks due to lamination or the like were not observed on the surface of the sintered body.

Example 3
A zirconia fine powder was obtained under the same conditions as in Example 2, except that after the calcined powder was washed with water, alumina sol was added so that the alumina content was 0.3 wt%. The characteristics of the zirconia fine powder are shown in Table 1.

  Subsequently, the zirconia fine powder obtained above was press-molded and sintered under the condition of 1350 ° C. Table 2 shows the characteristics of the obtained sintered body. The monoclinic phase rate after the deterioration test was 0%, and it was confirmed that the sintered body was extremely difficult to deteriorate. Further, when an impregnation test with a red dye was performed, scratches and cracks due to lamination or the like were not observed on the surface of the sintered body.

Example 4
Zirconia fine powder was obtained under the same conditions as in Example 2 except that 0.5% by weight of germanium oxide was added instead of alumina sol. The characteristics of the zirconia fine powder are shown in Table 1.

  Subsequently, the zirconia fine powder obtained above was press-molded and sintered under the condition of 1350 ° C. Table 2 shows the characteristics of the obtained sintered body. The monoclinic phase rate after the deterioration test was 0%, and it was confirmed that the sintered body was extremely difficult to deteriorate. Further, when an impregnation test with a red dye was performed, scratches and cracks due to lamination or the like were not observed on the surface of the sintered body.

Example 5
A zirconia fine powder was obtained under the same conditions as in Example 3 except that alumina content was 0.25 wt% and germanium oxide was added 0.25 wt% instead of alumina sol. The characteristics of the zirconia fine powder are shown in Table 1.

  Subsequently, the zirconia fine powder obtained above was press-molded and sintered at 1300 ° C. Table 2 shows the characteristics of the obtained sintered body. The monoclinic phase rate after the deterioration test was 0%, and it was confirmed that the sintered body was extremely difficult to deteriorate. Further, when an impregnation test with a red dye was performed, scratches and cracks due to lamination or the like were not observed on the surface of the sintered body.

Example 6
Zirconia fine powder was obtained under the same conditions as in Example 3 except that alumina content was 0.15 wt% and silica sol was 0.15 wt% instead of alumina sol. The characteristics of the zirconia fine powder are shown in Table 1.

  Subsequently, the zirconia fine powder obtained above was press-molded and sintered under the condition of 1350 ° C. Table 2 shows the characteristics of the obtained sintered body. The monoclinic phase rate after the deterioration test was 0%, and it was confirmed that the sintered body was extremely difficult to deteriorate. Further, when an impregnation test with a red dye was performed, scratches and cracks due to lamination or the like were not observed on the surface of the sintered body.

Example 7
The zirconia fine powder obtained in Example 3 was dispersed in water to obtain a zirconia slurry having a slurry concentration of 50%. After the viscosity was adjusted by adding a thickener to this slurry, spray granulation was performed. The obtained zirconia granules had an average particle size of 55 μm and a light bulk density of 1.20 g / cm ³ .

  Subsequently, the zirconia fine powder obtained above was press-molded and sintered under the condition of 1350 ° C. Table 2 shows the characteristics of the obtained sintered body. The monoclinic phase rate after the deterioration test was 0%, and it was confirmed that the sintered body was extremely difficult to deteriorate. Further, when an impregnation test with a red dye was performed, scratches and cracks due to lamination or the like were not observed on the surface of the sintered body.

Comparative Example 1
Zirconia fine powder was obtained under the same conditions as in Example 1 except that the calcining temperature in Example 1 was set to 900 ° C. The characteristics of the zirconia fine powder are shown in Table 1.

  Subsequently, the zirconia fine powder obtained above was press-molded and sintered under the condition of 1350 ° C. Table 2 shows the characteristics of the obtained sintered body. It was confirmed that the monoclinic phase ratio after the deterioration test was 0% and it was a sintered body that was not easily deteriorated. However, when the bending strength was low and an impregnation test with a red dye was performed, the surface of the sintered body was Scratches and cracks due to lamination and the like were observed, and it was found to be difficult to mold.

Comparative Example 2
A zirconia fine powder was obtained under the same conditions as in Example 1 except that the hydrolysis reaction time in Example 1 was changed to 200 hours. The reaction rate of the hydrated zirconia sol was 89%. The characteristics of the obtained fine zirconia powder are shown in Table 1, and the particle size distribution (frequency and cumulative curve) is shown in FIG.

  Next, the zirconia fine powder obtained above was press-molded and sintered under the conditions of 1350 ° C. and 1400 ° C., respectively, but the relative density of the obtained sintered body was as low as 97.3 and 98.6%. Further, the characteristics of the sintered body obtained by sintering at 1450 ° C., which is a higher temperature, were evaluated. The results are shown in Table 2. When an impregnation test with a red dye was performed, scratches and cracks due to lamination and the like were not observed on the surface of the sintered body, and the bending strength was high, but the monoclinic phase ratio after the deterioration test was 65. %, And it was found that the sintered body was extremely low in reliability and easily deteriorated.

Comparative Example 3
Zirconia fine powder was obtained under the same conditions as in Example 1 except that potassium hydroxide was not added to the aqueous zirconium salt solution of Example 1 and the calcining temperature was 1200 ° C. The characteristics of the obtained fine zirconia powder are shown in Table 1, and the particle size distribution (frequency and cumulative curve) is shown in FIG.

  Next, the zirconia fine powder obtained above was press-molded and sintered under the conditions of 1350-1500 ° C., but since the relative density of the obtained sintered body was lower than 98%, the temperature was higher. The characteristics of the sintered body obtained by sintering at 1550 ° C. were evaluated. The results are shown in Table 2. When an impregnation test with a red dye was performed, scratches and cracks due to lamination and the like were observed on the surface of the sintered body, the bending strength was low, and the monoclinic phase ratio after the deterioration test was 78%. It was found that the sintered body is easily deteriorated and has low reliability.

この表から、実施例の方が低温で焼結しても高い焼結体密度及び曲げ強度が得られる事が明らかである。

From this table, it is clear that even when the example is sintered at a lower temperature, a higher sintered body density and bending strength can be obtained.

The particle size distribution of the zirconia fine powder obtained in Example 2 is shown. The particle size distribution of the zirconia powder obtained by the comparative example 2 is shown. The particle size distribution of the zirconia powder obtained in Comparative Example 3 is shown.

Claims (10)

A zirconia fine powder containing at least one of yttria, calcia, magnesia and ceria as a stabilizer, the zirconia fine powder having a BET specific surface area of 5 to 10 m ² / g and an average particle size of 0.3 to 0.00. Zirconia fine powder in the range of 6 μm, and in the cumulative curve of the particle size distribution, the proportions of particles having a particle size of 0.2 μm, 1 μm and 2 μm are 0%, 95% or more and 100%, respectively. The fine zirconia powder according to claim 1, wherein the peak of the particle size distribution exists only in the range of 0.2 to 2 µm. The fine zirconia powder according to claim 1 or 2, which contains 2 to 4 mol% of yttria as a stabilizer and has a monoclinic phase ratio of 10 to 40%. The zirconia fine powder according to any one of claims 1 to 3, wherein the zirconia fine powder contains one or more additives. The zirconia fine powder according to claim 4, wherein the cation of the additive is a cation having an ionic radius smaller than that of zirconium ions and / or a cation having a valence other than tetravalent. The zirconia fine powder according to claim 4 or 5, wherein the cation of the additive is at least one cation selected from the group consisting of aluminum, silicon and germanium. In a method of obtaining a zirconia powder by drying, calcining, and pulverizing a hydrated zirconia sol obtained by hydrolysis of an aqueous zirconium salt solution, an alkali metal hydroxide and / or an alkaline earth metal hydroxide is added to the aqueous zirconium salt solution. And then adding one or more compounds of yttrium, calcium, magnesium and cerium as a stabilizer raw material to the hydrated zirconia sol obtained by hydrolysis until the reaction rate reaches 98% or more. Dry and calcinate in the range of 1000 to 1200 ° C. to obtain zirconia powder, and then use zirconia balls having a diameter of 3 mm or less so that the average particle diameter of the zirconia powder is in the range of 0.3 to 0.6 μm. 4. The method for producing a fine zirconia powder according to claim 1, wherein the powder is wet pulverized. The method for producing zirconia fine powder according to claim 7, wherein an additive is added to the hydrated zirconia sol or the powder obtained by calcining. . 9. The method for producing fine zirconia powder according to claim 7 or 8, wherein the yttrium compound is added in an amount of 2 to 4 mol% in terms of oxide. A zirconia granule obtained by spray granulating a zirconia fine powder according to claim 1 having a mean particle size of 30 to 80 μm and a light bulk density of 1.00 to 1.40 g / cm ³ .

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