JP6897088B2 - Orange zirconia sintered body and its manufacturing method - Google Patents

Description

The present invention relates to an orange-colored zirconia sintered body.

The zirconia sintered body exhibits arbitrary coloration by containing a lanthanoid rare earth oxide or a transition metal as a colorant (Patent Document 1). When the zirconia sintered body contains a colorant, the design is enhanced in addition to the original high-class feeling and mechanical strength of zirconia. Therefore, the zirconia sintered body containing a colorant (hereinafter, also referred to as "colored zirconia sintered body") has a wide range of applications such as decorative members and exterior members in addition to conventional optical applications, medical applications, and mechanical applications. It's coming. With the expansion of applications, colored zirconia sintered bodies are required to have more differentiated design properties. Furthermore, among the colored zirconia sintered bodies, the zirconia sintered bodies that exhibit bright colors such as red, pink, orange, purple, light blue, and light gray have a particularly strong influence on the design, so the color tone. The demands placed on the product are increasing.

For example, the following have been reported so far as zirconia sintered bodies exhibiting an orange color.

Patent Document 1 as a zirconia sintered body exhibiting an orange _color, and one of Y ₂ O 3, MgO or CaO, zirconia sintered body containing a CeO ₂ is disclosed.

Further, as an orange zirconia sintered body having no flesh color, a zirconia sintered body containing erbium oxide and terbium oxide or placeodium oxide has been reported (Patent Document 2).

Japanese Unexamined Patent Publication No. 62-59571 Japanese Unexamined Patent Publication No. 2011-020872

The orange-colored sintered body disclosed in Patent Documents 1 and 2 does not exhibit translucency. The color tone of the opaque sintered body is expressed only by the reflected light on the surface. The color tone of these sintered bodies changed significantly due to deterioration of the sintered body due to long-term use. Even if these sintered bodies do not have a decrease in strength or the like, the life of these sintered bodies that can be used as members is shortened due to changes in aesthetics.

Further, the color tone of the sintered body exhibiting translucency is expressed not only by the reflected light on the surface but also by the influence of the scattered light and the transmitted light inside the sintered body. Therefore, the change in color tone due to deterioration of the sintered body of the sintered body having translucency is larger than that of the opaque sintered body.

In view of these problems, it is an object of the present invention to provide a zirconia sintered body having translucency and exhibiting an orange color, which has a small change in color tone after long-term use. And.

The present inventors have investigated discoloration due to deterioration in use and suppression thereof in a colored zirconia sintered body. As a result, we have found a zirconia sintered body having a translucent property with a specific composition and exhibiting an orange color with almost no change in color tone even when used.

That is, in the present invention, the Al ₂ O ₃ content is 0.01% by weight or more and 1.0% by weight or less, and the balance is 1.2 mol% or more and 3.5 mol% or less of yttria and 0.005 mol% or more and 0.5 mol. It is a zirconia sintered body which is a zirconia containing% or less of placeodia.

Hereinafter, the zirconia sintered body of the present invention will be described.

The sintered body of the present invention has an Al ₂ O ₃ content of 0.01% by weight or more and 1.0% by weight or less, 0.03% by weight or more and 0.8% by weight or less, and further 0.04% by weight. It is preferably 0.6% by weight or more. If the alumina content is less than 0.01% by weight, the sintered body has low strength. On the other hand, when the Al ₂ O ₃ content exceeds 1.0% by weight, the density of the sintered body tends to decrease, which increases the individual difference in color tone. As a more preferable Al ₂ O ₃ content, 0.05% by weight or more and 0.3% by weight or less can be mentioned.

In the present invention, the Al ₂ O ₃ content can be determined from the weight ratio _{of Al 2} O _{3 to} the weight of the sintered body of the present invention.

The sintered body of the present invention _{contains zirconia containing yttria (Y 2} O ₃ ) and placeodia (Pr ₆ O ₁₁ ) (hereinafter, also referred to as “Y / Pr-containing zirconia”). The content of Y / Pr-containing zirconia may be 99% by weight or more and 99.99% by weight or less, 99.2% by weight or more and 99.97% by weight or less, and further 99.4% by weight or more and 99.96% by weight. The following is preferable.

In the present invention, the Y / Pr-containing zirconia content can be determined from the weight ratio of Y / Pr-containing zirconia to the weight of the sintered body of the present invention.

Y / Pr-containing _zirconia, a zirconia containing Y 2 _{O 3} and _Pr 6 _{O 11.}

Yttrium functions as a stabilizer without coloring zirconia. The yttria content of zirconia is preferably 1.2 mol% or more and 3.5 mol% or less, 1.3 mol% or more and 3.2 mol% or less, and more preferably 1.5 mol% or more and 3.0 mol% or less. If the yttria content is less than 1.2 mol%, the sintered body is likely to be destroyed during the production of the sintered body or under hydrothermal conditions. On the other hand, if the yttria content exceeds 3.5 mol%, not only the strength of the sintered body is lowered, but also the transparency becomes too high. If the transparency is too high, the coloration is weakened, so that the coloration tends to be different from the orange coloration.

In the present invention, the yttria content (mol%) can be determined from the molar ratio of yttria to the total of yttria, placeodia and zirconia in zirconia (Y ₂ O ₃ / (Y ₂ O ₃ + Pr ₆ O ₁₁ + ZrO ₂ )). it can.

Praseodymium mainly functions as a colorant. When zirconia contains placeodia, the sintered body of the present invention becomes orange. The placeodia content is preferably 0.005 mol% or more and 0.5 mol% or less, 0.007 mol% or more and 0.45 mol% or less, and more preferably 0.009 mol% or more and 0.4 mol% or less.

In the present invention, the placeodia content (mol%) can be determined from the molar ratio of placeodia to the total of yttria, placeodia and zirconia in zirconia (Pr ₆ O ₁₁ / (Y ₂ O ₃ + Pr ₆ O ₁₁ + ZrO ₂ )). it can.

The molar ratio of ytria content (mol%) to placeozia content (mol%) in zirconia (hereinafter referred to as "Y ₂ O ₃ / Pr ₆ O ₁₁ ratio") is 2 or more, further 4 or more, and Further, it is preferably 4.45 or more. Both yttria and placeodia have the effect of stabilizing the crystal phase of zirconia. However, the stabilizing effect is stronger in yttrium than in placeodia. Therefore, since the amount of yttria is larger than that of placeodia, the sintered body of the present invention is a sintered body having a more stable crystal phase and exhibiting an orange color. The Y ₂ O ₃ / Pr ₆ O ₁₁ ratio is arbitrary as long as the above-mentioned yttrium content and the above-mentioned placeodia content are satisfied, but _{the upper limit of the Y 2} O ₃ / Pr ₆ O ₁₁ ratio is 300, and further 100 or less. , And even 50 or less, and even 20 or less.

It is preferable that the zirconia crystal structure of the sintered body of the present invention contains tetragonal crystals, and the main phase of the crystal structure is tetragonal crystals. In order for the sintered body of the present invention to have a translucent color and an orange color tone, a tetragonal crystal that scatters light at the grain boundaries is indispensable. Further, in the zirconia crystal structure of the sintered body of the present invention, if the main phase is tetragonal, that is, if the tetragonal content is 50% or more, further 80% or more, and further 90% or more. It may contain cubic crystals, or may be a mixed crystal of tetragonal crystals and cubic crystals.

Since the average crystal grain size is appropriately small, the sintered body of the present invention has strength that can be used in various members and the like. Therefore, the average crystal grain size of the sintered body of the present invention is preferably 0.3 μm or more and 0.5 μm or less, and preferably 0.3 μm or more and 0.45 μm or less.

The sintered body of the present invention preferably has a relative density of 99.7% or more, more preferably 99.75% or more, and further preferably 99.80% or more. When the relative density is 99.7% or more, the sintered body of the present invention tends to have translucency. In the present invention, the relative density is the ratio of the measured density to the theoretical density. For the theoretical density, the density of the HIP-treated body obtained by primary sintering and HIP-treating the molded body having the same composition was used.

The measured density of the sintered body of the present invention varies depending on the composition, but is 6.080 g / cm ³ or more and 6.140 g / cm ³ or less, further 6.085 g / cm ³ or more and 6.135 g / cm ³ or less, and further. 6.090 g / cm ³ or more and 6.130 g / cm ³ or less.

The sintered body of the present invention has translucency. The sintered body of the present invention exhibits only surface reflected light by exhibiting a color tone expressed not only by surface reflected light but also by surface reflected light such as scattered light and transmitted light inside the sintered body and other light. Shows a more aesthetically pleasing tone than the color. In order to improve the aesthetics, the sintered body of the present invention has a total light transmittance (hereinafter, also simply referred to as “total light transmittance”) of 10% or more with respect to the light source D65 at a sample thickness of 1.0 mm, and further. It is preferably 13% or more, and more preferably 15% or more. On the other hand, if the translucency becomes too high, the color tone tends to be weakened. Therefore, the total light transmittance is preferably less than 35%. Preferred total light transmittance is 10% or more and less than 35%, further 10% or more and 32% or less, and further 10% or more and 26% or less.

The sintered body of the present invention exhibits an orange color. Such a color tone can be confirmed by checking that the brightness L ^* is 45 or more and 75 or less, a ^* is 0 or more and 35 or less, and b ^* is 35 or more and 75 or less in the ^{L *} a ^* b ^{* color system.} More preferable color tones include lightness L ^* of 50 or more and 70 or less, a ^* of 2 or more and 30 or less and b ^* of 40 or more and 70 or less, lightness L ^* of 55 or more and 70 or less, a ^* of 5 or more and 25 or less, and b ^*. Is 45 or more and 65 or less.

The sintered body of the present invention does not change in color due to long-term use. It can be confirmed by measuring the color tone of the sintered body before and after use that there is no change in color tone. In particular, it may be confirmed that there is no change in color tone due to the color tone difference obtained by the following formula from the color tone of the sintered body immersed in hot water at 140 ° C. for 24 hours and the color tone of the sintered body before immersion.

Color difference ΔE = {(L ₁ ^* -L ₂ ^* ) ² + (a ₁ ^* -a ₂ ^* ) ²
+ (B ₁ ^* −b ₂ ^* ) ² } ^0.5
In the above formula, L ₁ ^* , a ₁ ^*, and b ₁ ^{* are the lightness L *} , saturation a ^*, and b ^* of the sintered body before immersion, respectively. L ₂ ^* , a ₂ ^* and b ₂ ^{* are the lightness L *} , saturation a ^* and b ^* of the sintered body after immersion, respectively.

In the sintered body of the present invention, ΔE obtained by the above formula is 2.0 or less, and preferably 1.8 or less. If ΔE is 2.0 or less, the change in aesthetics cannot be recognized by visual observation. Theoretically, the lower limit of ΔE is 0, but ΔE may be 0.2 or more in consideration of measurement error and the like.

Examples of the three-point bending strength of the sintered body of the present invention include 1000 MPa or more, and further 1050 MPa or more. If the strength is too high, the workability will be low. Therefore, the three-point bending strength of the zirconia sintered body of the present invention may be 1300 MPa or less, more preferably 1250 MPa or less.

In the present invention, the three-point bending strength can be measured by a method according to ISR 1601.

Next, the method for producing the sintered body of the present invention will be described.

The sintered body of the present invention includes aluminum oxide of 0.01% by weight or more and 1.0% by weight or less, yttria with a balance of 1.2 mol% or more and 3.5 mol% or less, and 0.005 mol% or more and 0.5 mol. It can be produced by a production method having a sintering step of sintering a molded product which is zirconia containing% or less of placeozia at 1350 ° C. or higher and 1500 ° C. or lower.

The molded product to be subjected to the sintering step includes aluminum oxide of 0.01% by weight or more and 1.0% by weight or less, yttria with a balance of 1.2 mol% or more and 3.5 mol% or less, and 0.005 mol% or more and 0. It is a zirconia containing 5 mol% or less of placeodia. More preferable molded bodies include aluminum oxide of 0.03% by weight or more and 0.8% by weight or less, yttria having a balance of 1.3 mol% or more and 3.2 mol% or less, and 0.007 mol% or more and 0.45 mol% or less. It is mentioned that it is a zirconia containing the placeodia of.

The content of aluminum oxide, alumina _(Al 2 _{O 3)} and aluminum oxide in terms, to the total weight of the zirconia containing yttria and Puraseojia (Y / Pr-containing zirconia), alumina _(Al 2 _{O 3)} in terms It can be obtained as the weight ratio of the aluminum oxide.

The shape of the molded body is arbitrary, and at least one of a group consisting of a disk shape, a columnar shape, a plate shape, a spherical shape, and a substantially spherical shape can be exemplified.

The molded product is obtained by molding a raw material powder containing Y / Pr-containing zirconia and aluminum oxide in the above composition.

The raw material powder preferably has the above composition and has an average particle size of 0.35 μm or more and 0.60 μm, and more preferably 0.40 μm or more and 0.55 μm or less. The BET specific surface area is preferably ⁵ to 15 m 2 / g, more preferably 7 to 13 m ² / g.

The raw material powder is preferably spray granulated powder granules (hereinafter, also simply referred to as “powder granules”), and is preferably powder granules containing an organic binder. By using the raw material powder as powder granules, the fluidity when forming the molded product is increased, and pores are easily removed from the molded product. This makes it difficult for bubbles to be generated in the sintered body.

Examples of the organic binder include at least one organic binder in the group consisting of commonly used polyvinyl alcohol, polyvinyl butyrate, wax and acrylic. The content of the organic binder in the powder granules may be 1% by weight or more and 5% by weight or less with respect to the raw material powder.

If starting powders and powder granules, preferably has an average granule diameter is 30μm or more 80μm or less, the bulk density is preferably at 1.10 g / cm ³ or more 1.40 g / cm ³ or less.

The Y / Pr-containing zirconia contained in the raw material powder may be any zirconia powder containing _{yttria (Y 2} O ₃ ) and placeodia (Pr ₆ O _11). Further, the Y / Pr-containing zirconia may be at least two powders in the group consisting of yttria-containing zirconia, placeozia-containing zirconia, and yttria-placeodia-containing zirconia, and further, a mixed powder of yttria-containing zirconia and yttria-placeodia-containing zirconia. It may be. Compared with the mixed powder of itria powder and placeodia powder and zirconia powder, or the mixed powder of itria-containing zirconia powder and placeodia powder, the baking obtained by using the zirconia powder containing itria and placeodia before sintering The color tone of the body tends to be uniform. The Y / Pr-containing zirconia is particularly preferably at least one of a mixed powder of yttria-containing zirconia and yttria-placeodia-containing zirconia, or yttria-placeodia-containing zirconia powder.

The Y / Pr-containing zirconia powder preferably has an yttria content of 1.2 mol% or more and 3.5 mol% or less, further preferably 1.3 mol% or more and 3.2 mol% or less, and a placeodia content of 0.005 mol. % Or more and 0.5 mol% or less, and more preferably 0.007 mol% or more and 0.45 mol% or less. When the Y / Pr-containing zirconia contains yttria-containing zirconia powder, the yttria content of the yttria-containing zirconia powder is 2 mol% or more and 4 mol% or less, and further 2 mol% or more and 3.5 mol% or less. When the Y / Pr-containing zirconia contains the placeodia-containing zirconia powder, the placeodia content of the placeodia-containing zirconia powder may be 0.05 mol% or more and 1.0 mol% or less.

The preferable aluminum oxide contained in the raw material powder is preferably at least one powder in the group consisting of alumina, hydrated alumina, alumina sol, aluminum hydroxide, aluminum chloride, aluminum nitrate and aluminum sulfate, and alumina and hydrated. It is preferably at least one powder in the group consisting of alumina and alumina sol.

As the raw material powder, Y / Pr-containing zirconia and aluminum oxide may be mixed by any method.

The raw material powder may have an aluminum oxide content of 0.01% by weight or more and 1.0% by weight or less, and the balance may be Y / Pr-containing zirconia, and the raw material powder has an aluminum oxide content of 0. It may be .03% by weight or more and 0.8% by weight or less, and the balance may be Y / Pr-containing zirconia.

As a particularly preferable raw material powder, it is particularly preferable that it is a mixed powder of yttria-containing zirconia and yttria-stabilia-containing zirconia, or at least one of the yttria-stabilia-containing zirconia powder and an alumina powder.

The molded product is obtained by molding the raw material powder, and may be molded after crushing the raw material powder. The molding method may be any method as long as the raw material powder can be molded into a desired shape, and examples thereof include at least one of a group consisting of a mold press, a cold hydrostatic press, slip casting and injection molding.

In the sintering step, the molded product is sintered in an oxidizing atmosphere and at a sintering temperature of 1350 ° C. or higher and 1500 ° C. or lower. As a result, the sintered body of the present invention can be obtained.

Sintering is performed in an oxidizing atmosphere. By sintering in an oxidizing atmosphere, the sintered body of the present invention has translucency and exhibits an orange color. In a reducing atmosphere, an inert atmosphere, and a vacuum atmosphere, the oxidation state of placeodium changes, so that the obtained sintered body exhibits a color other than orange. As the oxidizing atmosphere, either an oxygen gas atmosphere or an air atmosphere can be mentioned. Since it is simple, it is preferable to have an atmospheric atmosphere.

The sintering temperature is preferably 1400 ° C. or higher and 1490 ° C. or lower, further preferably 1410 ° C. or higher and 1480 ° C. or lower, and further preferably 1420 ° C. or higher and 1470 ° C. or lower.

The heating rate is 800 ° C./hour or less, and further 650 ° C./hour or less. Preferred heating rates include 50 ° C./hour or more and 800 ° C./hour or less, and further 100 ° C./hour or more and 700 ° C./hour or less. As a result, the progress of sintering in the heating process can be suppressed, and the molded product can be sintered at the sintering temperature.

The holding time at the sintering temperature (hereinafter, also simply referred to as “holding time”) may be an arbitrary time depending on the sintering temperature. Examples of the holding time include 5 hours or less, further 3 hours or less, and further 2 hours or less.

The sintering method is preferably atmospheric pressure sintering. Atmospheric pressure sintering is a method of sintering by simply heating a molded product without applying an external force. Specific examples of normal pressure sintering include sintering under atmospheric pressure.

The production method of the present invention may include at least one of a polishing step of polishing the sintered body and a processing step of processing the shape. The polishing step polishes the surface of the sintered body after sintering. By polishing, it is possible to obtain a sintered body having a surface condition suitable for the intended use, such as imparting a glossy feeling to the surface. In the processing process, the sintered body is processed into an arbitrary shape. As a result, the sintered body can be shaped according to the application. Either the polishing step or the processing step may be performed first.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a zirconia sintered body having translucency and exhibiting an orange color, which has a small change in color tone after long-term use.

Hereinafter, the present invention will be specifically described with reference to Examples. However, the present invention is not limited to these examples.

(Average particle size)
The average particle size of the powder sample was measured using a Microtrack particle size distribution meter (device name: 9320-HRA, manufactured by Honeywell). As a pretreatment, the sample powder was suspended in distilled water to form a slurry, which was then dispersed for 3 minutes using an ultrasonic homogenizer (device name: US-150T, manufactured by Nippon Seiki Seisakusho).

The "average particle size" related to the zirconia powder in the present invention is a particle whose cumulative curve of the particle size distribution expressed on a volume basis is the median value (median diameter; particle size corresponding to 50% of the cumulative curve). The diameter of a sphere with the same volume as the above, which is measured by a particle size distribution measuring device by a laser diffraction method.

(Average granule diameter)
The average granule diameter of the granule sample was determined by the sieving test method.

(Average crystal grain size of sintered body)
The average crystal grain size of the sintered sample was determined by the planimetric method from the SEM photograph obtained by the field emission scanning electron microscope (FESEM). That is, the mirror-polished sintered body sample was thermally etched and observed using a field emission scanning electron microscope (device name: JSM-T220, manufactured by JEOL Ltd.). The average crystal grain size was calculated from the obtained SEM photographs by the planimetric method.

(Density of sintered body)
The measured density of the sintered sample was determined by the Archimedes method. A HIP-treated body having the same composition as the sintered body sample was prepared, and the measured density of the HIP-treated body was determined by the Archimedes method and used as the theoretical density. The relative density of the sintered body sample was obtained from the ratio of the measured density of the sintered body to the theoretical density.

(Total light transmittance)
The total light transmittance of the sintered body sample was measured by a turbidity meter (device name: NDH2000, manufactured by Nippon Denshoku Co., Ltd.) by a method conforming to JIS K7361. A disk-shaped sintered body having a thickness of 1 mm, which had been polished on both sides, was used as a measurement sample.

(Color tone)
The color tone of the sintered sample was measured by a method conforming to JIS Z 8729. A color difference meter (device name: Z-300, manufactured by Nippon Denshoku Co., Ltd.) was used for the measurement.

For measurement use, a disk-shaped sintered body having a thickness of 2.8 mm, which had been polished on one side, was used. The color tone was measured on the polished surface of the sintered body.

(Strength)
The three-point bending strength of the sintered sample was measured by the three-point bending measurement method according to JIS R 1601.

Example 1
A hydrated zirconia sol was obtained by hydrolyzing an aqueous solution of zirconium oxychloride. _{Yttria (Y 2} O ₃ ) and placeodia (Pr ₆ O ₁₁ ) are added to the hydrated zirconia sol so that the yttria concentration is 1.30 mol% and the placeodia concentration is 0.24 mol%, and then dried and calcined. , Yttria and placeodia-containing zirconia calcined powder was obtained. The calcining conditions were 1160 ° C. for 2 hours in the air. The obtained calcined powder was washed with distilled water and then dried to obtain a Y / Pr-containing zirconia powder. A mixed powder obtained by adding α-alumina having an average particle size of 0.3 μm to the Y / Pr-containing zirconia powder so that the _{Al 2} O _{3 content is 0.05% by weight based on the weight of the Y / Pr-containing zirconia powder.} And said.

Distilled water was added to the mixed powder to obtain a slurry having a powder content of 45% by weight, which was pulverized with a ball mill. The ball mill used a zirconia ball having a diameter of 2 mm as a pulverization medium in an aqueous solvent, and the treatment time was 12 hours.

The average particle size and BET specific surface area of the powder in the slurry after the pulverization treatment (hereinafter, also referred to as “pulverized slurry”) were measured. The BET specific surface area was measured on the zirconia powder after the pulverized slurry was dried in the air at 110 ° C. The average particle size was 0.44 μm and the BET specific surface area was 14.2 m ² / g.

After adding 3% by weight of an organic binder to the pulverized slurry, this was spray-dried to obtain powdered granules. The powder granules had an average granule diameter of 43 μm and a light bulk density of 1.25 g / cm ³ .

The obtained granules were premolded with a 19.6 MPa uniaxial press and then subjected to a cold hydrostatic press (hereinafter, also referred to as “CIP”) at 196 MPa to obtain a molded product. The obtained molded product was sintered at normal pressure in an air atmosphere at a sintering temperature of 1450 ° C., a heating rate of 600 ° C./hr, and a holding time of 2 hours to obtain a zirconia sintered body of this example. The obtained zirconia sintered body had translucency and had an orange color.

The composition of the Y / Pr-containing zirconia powder is shown in Table 1, and the evaluation results of the zirconia sintered body of this example are shown in Tables 2 and 3.

Example 2
A pulverized slurry and powder granules were obtained in the same manner as in Example 1 except that yttria and placeodia were added to the hydrated zirconia sol so that the yttria concentration was 1.69 mol% and the placeodia concentration was 0.37 mol%.

The powder in the pulverized slurry had an average particle size of 0.45 μm and a BET specific surface area of 13.5 m ² / g, and the powder granules had an average granule diameter of 46 μm and a light bulk density of 1.27 g / cm ³ . ..

The zirconia sintered body of this example was obtained by molding and sintering in the same manner as in Example 1 except that the obtained powder granules were used. The obtained zirconia sintered body had translucency and had an orange color.

The composition of the Y / Pr-containing zirconia powder is shown in Table 1, and the evaluation results of the zirconia sintered body of this example are shown in Tables 2 and 3.

Example 3
Yttria and placeodia were added to the hydrated zirconia sol so that the yttria concentration was 1.59 mol% and the placeodia concentration was 0.24 mol%, the calcining temperature was set to 1190 ° C, and the crushing time was set to 24 hours. A crushed slurry and powder granules were obtained in the same manner as in Example 1 except for the above.

The powder in the pulverized slurry had an average particle size of 0.44 μm and a BET specific surface area of 12.8 m ² / g, and the powder granules had an average granule diameter of 45 μm and a light bulk density of 1.25 g / cm ³ . ..

The zirconia sintered body of this example was obtained by molding and sintering in the same manner as in Example 1 except that the obtained powder granules were used and the sintering temperature was set to 1400 ° C. The obtained zirconia sintered body had translucency and had an orange color.

The composition of the Y / Pr-containing zirconia powder is shown in Table 1, and the evaluation results of the zirconia sintered body of this example are shown in Tables 2 and 3.

Example 4
Yttria and placeodia were added to the hydrated zirconia sol so that the yttria concentration was 1.59 mol% and the placeodia concentration was 0.24 mol%, the calcining temperature was set to 1190 ° C, and the crushing time was set to 24 hours. A crushed slurry and powder granules were obtained in the same manner as in Example 1 except for the above.

The powder in the pulverized slurry had an average particle size of 0.44 μm and a BET specific surface area of 12.8 m ² / g, and the powder granules had an average granule diameter of 45 μm and a light bulk density of 1.25 g / cm ³ . ..

The zirconia sintered body of this example was obtained by molding and sintering in the same manner as in Example 1 except that the obtained powder granules were used. The obtained zirconia sintered body had translucency and had an orange color.

The composition of the Y / Pr-containing zirconia powder is shown in Table 1, and the evaluation results of the zirconia sintered body of this example are shown in Tables 2 and 3.

Example 5
Yttria and placeodia were added to the hydrated zirconia sol so that the yttria concentration was 1.59 mol% and the placeodia concentration was 0.24 mol%, the calcining temperature was set to 1190 ° C, and the amount of α-alumina added was 0. A crushed slurry and powder granules were obtained in the same manner as in Example 1 except that the crushing time was set to .15% by weight and the crushing time was set to 24 hours.

The powder in the pulverized slurry had an average particle size of 0.45 μm and a BET specific surface area of 13.0 m ² / g, and the powder granules had an average granule diameter of 44 μm and a light bulk density of 1.23 g / cm ³ . ..

The zirconia sintered body of this example was obtained by molding and sintering in the same manner as in Example 1 except that the obtained powder granules were used. The obtained zirconia sintered body had translucency and had an orange color.

The composition of the Y / Pr-containing zirconia powder is shown in Table 1, and the evaluation results of the zirconia sintered body of this example are shown in Tables 2 and 3.

Example 6
Yttria and placeodia were added to the hydrated zirconia sol so that the yttria concentration was 1.59 mol% and the placeodia concentration was 0.24 mol%, the calcining temperature was set to 1190 ° C, and the amount of α-alumina added was 0. A crushed slurry and powder granules were obtained in the same manner as in Example 1 except that the crushing time was set to .25% by weight and the crushing time was set to 24 hours.

The powder in the pulverized slurry had an average particle size of 0.46 μm and a BET specific surface area of 12.7 m ² / g, and the powder granules had an average granule diameter of 47 μm and a light bulk density of 1.23 g / cm ³ .

The zirconia sintered body of this example was obtained by molding and sintering in the same manner as in Example 1 except that the obtained powder granules were used. The obtained zirconia sintered body had translucency and had an orange color.

The composition of the Y / Pr-containing zirconia powder is shown in Table 1, and the evaluation results of the zirconia sintered body of this example are shown in Tables 2 and 3.

Example 7
Yttria and placeodia were added to the hydrated zirconia sol so that the yttria concentration was 1.59 mol% and the placeodia concentration was 0.24 mol%, the calcining temperature was set to 1190 ° C, and the amount of α-alumina added was 0. A crushed slurry and powder granules were obtained in the same manner as in Example 1 except that the crushing time was set to 5.5% by weight and the crushing time was set to 24 hours.

The powder in the pulverized slurry had an average particle size of 0.46 μm and a BET specific surface area of 12.8 m ² / g, and the powder granules had an average granule diameter of 42 μm and a light bulk density of 1.28 g / cm ³ . ..

The zirconia sintered body of this example was obtained by molding and sintering in the same manner as in Example 1 except that the obtained powder granules were used. The obtained zirconia sintered body had translucency and had an orange color.

The composition of the Y / Pr-containing zirconia powder is shown in Table 1, and the evaluation results of the zirconia sintered body of this example are shown in Tables 2 and 3.

Example 8
A hydrated zirconia sol was obtained by hydrolyzing an aqueous solution of zirconium oxychloride. Yttria was added to the hydrated zirconia sol so that the yttria concentration was 3 mol%, and then dried and calcined to obtain a zirconia calcined powder containing yttria. The calcining condition was 1100 ° C. for 2 hours in the air. The obtained calcined powder was washed with distilled water and dried to obtain an yttria-containing zirconia powder.

A pulverized slurry and powder granules were obtained in the same manner as in Example 1 except that the obtained yttria-containing zirconia powder was used.

The powder in the pulverized slurry had an average particle size of 0.42 μm and a BET specific surface area of 13.1 m ² / g, and the average granule diameter of the powder granules was 45 μm and the light bulk density was 1.27 g / cm ³ .

The obtained powder granules and the powder granules obtained in the same manner as in Example 5 were stirred and mixed so as to have the following composition to obtain mixed powder granules.

Al ₂ O ₃ : 0.13% by weight
Y / Pr-containing zirconia: balance The composition of Y / Pr-containing zirconia in the mixed powder granules _{was 1.94 mol% for Y 2} O ₃ , 0.18 mol% for Pr ₆ O _{11 , and Zr O 2} for the balance.

A sintered body of this example was obtained by molding and sintering in the same manner as in Example 1 except that the obtained mixed powder granules were used. The obtained zirconia sintered body had translucency and had an orange color.

The composition of Y / Pr-containing zirconia in the mixed powder granules is shown in Table 1, and the evaluation results of the zirconia sintered body of this example are shown in Tables 2 and 3.

Example 9
A sintered body of this example was obtained in the same manner as in Example 8 except that the mixed powder granules had the following composition.

Al ₂ O ₃ : 0.1% by weight
Y / Pr-containing zirconia: balance The composition of Y / Pr-containing zirconia in the mixed powder granules was 2.30 mol% for _{Y 2} O ₃ , 0.12 mol% for _{Pr 6} O _{11 , and Zr O 2} for the balance. ..

The obtained zirconia sintered body had translucency and had an orange color.

The composition of Y / Pr-containing zirconia in the mixed powder granules is shown in Table 1, and the evaluation results of the zirconia sintered body of this example are shown in Tables 2 and 3.

Example 10
A sintered body of this example was obtained in the same manner as in Example 8 except that the mixed powder granules had the following composition.

Al ₂ O ₃ : 0.1% by weight
Y / Pr-containing zirconia: balance The composition of Y / Pr-containing zirconia in the mixed powder granules was 2.65 _{mol% for Y 2} O ₃ , 0.06 mol% for _{Pr 6} O _{11 , and Zr O 2} for the balance. ..

The obtained zirconia sintered body had translucency and had an orange color.

The composition of Y / Pr-containing zirconia in the mixed powder granules is shown in Table 1, and the evaluation results of the zirconia sintered body of this example are shown in Tables 2 and 3.

Example 11
A sintered body of this example was obtained in the same manner as in Example 8 except that the mixed powder granules had the following composition.

Al ₂ O ₃ : 0.055% by weight
Y / Pr-containing zirconia: balance The composition of Y / Pr-containing zirconia in the mixed powder granules was 2.93 _{mol% for Y 2} O ₃ , 0.01 mol% for _{Pr 6} O _{11 , and Zr O 2} for the balance. ..

The obtained zirconia sintered body had translucency and had an orange color.

The composition of Y / Pr-containing zirconia in the mixed powder granules is shown in Table 1, and the evaluation results of the zirconia sintered body of this example are shown in Tables 2 and 3.

Example 12
Yttria-containing zirconia powder was obtained in the same manner as in Example 8 except that the calcination conditions were set to 1150 ° C. for 2 hours in the air. A pulverized slurry and powder granules were obtained in the same manner as in Example 1 except that the obtained yttria-containing zirconia powder was used and the amount of α-alumina added was 0.25% by weight.

The powder in the pulverized slurry had an average particle size of 0.52 μm and a BET specific surface area of 7.2 m ² / g, and the average granule diameter of the powder granules was 47 μm and the light bulk density was 1.22 g / cm ³ .

The obtained powder granules and the powder granules obtained in the same manner as in Example 5 were stirred and mixed so as to have the following composition to obtain mixed powder granules.

Al ₂ O ₃ : 0.2% by weight
Y / Pr-containing zirconia: balance The composition of Y / Pr-containing zirconia in the mixed powder granules was 2.30 mol% for _{Y 2} O ₃ , 0.12 mol% for _{Pr 6} O _{11 , and Zr O 2} for the balance. ..

Molded and sintered in the same manner as in Example 1 except that the obtained mixed powder granules were used, premolding was performed at 98 MPa, and the heating rate was set to 100 ° C./hr. The sintered body of the example was obtained. The obtained zirconia sintered body had translucency and had an orange color.

The composition of Y / Pr-containing zirconia in the mixed powder granules is shown in Table 1, and the evaluation results of the zirconia sintered body of this example are shown in Tables 2 and 3.

Comparative Example 1
Yttria-containing zirconia powder, pulverized slurry and powder granules were obtained in the same manner as in Example 1 except that the placeodia was added to the hydrated zirconia sol so that the placeodia concentration was 0.5 mol%.

The powder in the pulverized slurry had an average particle size of 0.41 μm and a BET specific surface area of 14.5 m ² / g, and the powder granules had an average granule diameter of 43 μm and a light bulk density of 1.28 g / cm ³ . ..

The zirconia sintered body of this comparative example was prepared by molding and sintering in the same manner as in Example 1 except that the obtained powder granules were used. However, in this comparative example, cracks were generated during sintering, and a sintered body that maintained its shape could not be obtained. The results are shown in Tables 1 and 2.

Comparative Example 2
Yttria-containing zirconia powder, pulverized slurry and powder granules were obtained in the same manner as in Comparative Example 1 except that the placeodia was added to the hydrated zirconia sol so that the placeodia concentration was 1 mol%.

The powder in the pulverized slurry had an average particle size of 0.43 μm and a BET specific surface area of 14.8 m ² / g, and the powder granules had an average granule diameter of 45 μm and a light bulk density of 1.27 g / cm ³ . ..

A sintered body of this Comparative Example was produced by molding and sintering in the same manner as in Comparative Example 1 except that the obtained powder granules were used. However, in this comparative example, cracks were generated during sintering, and a sintered body that maintained its shape could not be obtained. The results are shown in Tables 1 and 2.

Comparative Example 3
Y / Pr-containing zirconia powder, pulverized slurry and the same method as in Comparative Example 1 except that yttria and placeodia were added to the hydrated zirconia sol so that the yttria concentration was 1.10 mol% and the placeodia concentration was 0.24 mol%. Powdered granules were obtained.

The powder in the pulverized slurry had an average particle size of 0.41 μm and a BET specific surface area of 13.6 m ² / g, and the powder granules had an average granule diameter of 46 μm and a light bulk density of 1.27 g / cm ³ . ..

A sintered body of this Comparative Example was produced by molding and sintering in the same manner as in Comparative Example 1 except that the obtained granules were used. However, in this comparative example, cracks were generated during sintering, and a sintered body that maintained its shape could not be obtained. The results are shown in Tables 1 and 2.

Comparative Example 4
Yttria and placeodia were added to the hydrated zirconia sol so that the yttria concentration was 1.59 mol% and the placeodia concentration was 0.24 mol%, the calcining temperature was set to 1190 ° C., and α-alumina was not added. A crushed slurry and powder granules were obtained in the same manner as in Example 1 except that the crushing time was 24 hours.

The powder in the pulverized slurry had an average particle size of 0.45 μm and a BET specific surface area of 12.8 ^{m 2} / g, and the powder granules had an average granule diameter of 43 μm and a light bulk density of 1.26 g / cm ³ . ..

A zirconia sintered body of this comparative example was obtained by molding and sintering in the same manner as in Example 1 except that the obtained powder granules were used. The results are shown in Tables 1 to 3.

(Measurement of color change ΔE)
The sintered bodies of Examples 1 to 12 and the sintered bodies of Comparative Example 4 were each immersed in hot water at 140 ° C. for 24 hours, and the color tones of the sintered bodies before and after the immersion were measured to determine the color tone difference ΔE. The results are shown in Table 4.

From Table 4, in each of the examples, the color tone difference ΔE was 2.0 or less, and no visual change in color tone was confirmed. On the other hand, in Comparative Example 4, the color tone difference ΔE was 4.4, and a change in color tone was visually observed.

The zirconia sintered body of the present invention is not only a structural material such as a crushed member, a dental member such as a dental prosthesis material and a color tone adjusting material thereof, but also a member such as a jewelry or a decorative member, for example, a watch part or a portable material. It can be used for exterior parts of electronic devices and various members.

Claims (2)

Zirconia containing 0.01% by weight or more and 1.0% by weight or less of aluminum oxide, and the balance of 1.2 mol% or more and 3.5 mol% or less of itria and 0.005 mol% or more and 0.5 mol% or less of placeodia. _{The Al 2} O ₃ content is 0.01% by weight or more and 1.0% by weight or less, and the balance is 1.0% by weight or less , which comprises a sintering step of sintering the molded product in an oxidizing atmosphere at 1350 ° C. or higher and 1500 ° C. or lower. Zirconia containing 1.2 mol% or more and 3.5 mol% or less of itria and 0.005 mol% or more and 0.5 mol% or less of placeozia, and the total light transmittance with respect to the light source D65 at a sample thickness of 1.0 mm is 10%. In the above method for producing a zirconia sintered body, the molded product is a mixed powder of zirconia containing itria and zirconia containing itria / placeodia, or at least one of zirconia powder containing itria / placeodia, and an alumina powder. der Ru Manufacturing method obtained by molding a mixed powder. The manufacturing method according to claim 1 , wherein the sintering method in the sintering step is atmospheric pressure sintering.