JP2014088319A - Light transmitting zirconia sintered body and manufacturing method and use thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a zirconia sintered body having high sintered body density and strength and excellent in light-transmitting, and to provide a method of manufacturing the zirconia sintered body with simple process by normal pressure sintering.SOLUTION: A light transmitting zirconia sintered body containing yttria of 2 to 4 mol% as a stabilizer, consisting of zirconia containing alumina of 0.1 to 0.2 wt.% as an additive agent, and having a relative density of 99.8% or more and a light transmittance with thickness of 1.0 mm of 35% or more is obtained by normal pressure sintering. It is preferable to sinter a powder containing alumina having a particle diameter of 0.01 to 0.5 μm of 0.1 to 0.2 wt.%, and having a BET specific surface area of 5 to 15 m/gm, an average particle size of 0.3 to 0.7 μm, a sinter shrinkage rate during normal sintering (▵ρ/▵T: g/cm°C) of 0.0125 to 0.0160 under normal pressure in atmosphere.

Description

  The present invention relates to a zirconia sintered body that is sintered under normal pressure, has a high density and strength, and is excellent in translucency. It is particularly suitable for use as a zirconia sintered body used in dental applications, a mill blank such as a denture material, and an orthodontic bracket.

A zirconia sintered body in which a small amount of Y ₂ O ₃ is dissolved as a stabilizer has high strength and high toughness, so that it is used as a material for mechanical structures such as cutting tools, dies, nozzles, and bearings, and as a biomaterial such as dental materials. Widely used. In the case of dental materials, not only mechanical properties such as high strength and high toughness but also optical properties such as translucency and color tone are required from an aesthetic point of view.

  Zirconia single crystals have translucency, and conventionally zirconia single crystals (cubic zirconia) containing about 10 mol% of yttria have been used for jewelry and the like, but have a problem of extremely low strength. On the other hand, it is known that a normal zirconia sintered body which is a polycrystalline body has no translucency. It is known that the pores existing between and within the grains cause light scattering as a cause of this, and so far, by reducing the pores, that is, by increasing the density of the sintered body, it becomes a polycrystalline zirconia sintered body. Research has been done to give transparency.

For example, Patent Document 1 discloses translucent zirconia containing ₂ mol% or more of Y ₂ O ₃ and ₃ to 20 mol% of TiO ₂ , but contains a large amount of TiO ₂ to provide translucency, There was a problem with strength.

Patent Document 2 discloses a zirconia sintered body having a translucent sintered body density of 99.8% in a composition of ₃ mol% Y ₂ O ₃ and 0.25 wt% Al ₂ O ₃ , and has a total light beam for visible light. The transmittance is reported to be 49% (thickness 0.5 mm). However, the sintered body was obtained by pressure sintering using a hot isostatic press (HIP), and sufficient translucency was not obtained by atmospheric pressure sintering.

JP-A-62-91467 Japanese Patent Laid-Open No. 20-50247

  The present invention eliminates the above-mentioned drawbacks in the conventional method, provides a sintered body having a high density and strength, and excellent translucency. In particular, such a zirconia sintered body is provided. An object of the present invention is to provide a method that can be manufactured by a simple process by atmospheric pressure sintering.

  As a result of detailed investigations on the relationship between the state of alumina in the zirconia powder, the sintered body density, and the total light transmittance of the sintered body, the present inventors have found that the pressureless sintering is merely achieved by increasing the sinterability of the zirconia powder. It is not possible to obtain a light-transmitting zirconia sintered body by sintering, and in order to obtain a light-transmitting zirconia sintered body by atmospheric pressure sintering, it is necessary to control the sintering speed of a specific temperature region of the zirconia In addition, the inventors have found that it is necessary to control the sintering speed depending on the physical properties of alumina used as an additive, and have completed the present invention.

That is, the present invention
1) Powder for translucent zirconia sintered body containing 2 to 4 mol% of yttria as a stabilizer and 0.1 to 0.2 wt% of alumina having a particle diameter of 0.01 to 0.5 µm as an additive.
2) The powder according to 1) above, wherein the BET specific surface area is 5 to 15 m ² / g and the average particle size is 0.3 to 0.7 μm.
3) Sintering shrinkage rate (Δρ / ΔT: g / cm ³ · ° C.) from 70% to 90% relative density in atmospheric pressure sintering (in the atmosphere, temperature rising rate 300 ° C./hour) is 0.0125. The powder according to any one of 1) to 2) above, which is 0.0160 or less,
It consists of

  Conventionally, it has been known to use fine alumina (sol etc.) for high-density zirconia sintered body, but its addition amount exceeds 0.2 wt% from the viewpoint of improving the characteristics required of the sintered body. However, a zirconia sintered body containing a large amount of different component alumina has no sufficient translucency even at high density due to the effects of light refraction and scattering. The sintered body of the present invention is a sintered body excellent in basic characteristics required for a sintered body and having excellent translucency in a range where the content of fine alumina is 0.2 wt% or less. .

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

  The “average particle size” related to the zirconia powder in the present invention is a particle having a median value (median diameter; particle size corresponding to 50% of the cumulative curve) of the cumulative particle size distribution expressed by volume. Is the diameter of a sphere having the same volume as that 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).

  “Monoclinic phase ratio (fm)” 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 intensity of the (111) plane is obtained, and the value calculated by the following formula 1 is used.

(However, 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.)
“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 “relative density” is a ratio (%) of (ρ / ρ ₀ ) × 100 using the measured density ρ actually measured by the Archimedes method and the theoretical density ρ ₀ obtained by the calculation formula of Equation 2 shown below. The value expressed in terms of. In Formula 2, the theoretical density of alumina was 3.987 (g / cm ³ ), and the theoretical density of 3 mol% yttria-containing zirconia was 6.0956 (g / cm ³ ).

{However, X: Alumina content (wt%)}
The translucent zirconia sintered body of the present invention contains 2 to 4 mol% yttria as a stabilizer. If the stabilizer is less than 2 mol%, not only the strength is lowered, but also the crystal phase becomes unstable, making it difficult to produce a sintered body. On the other hand, when the amount exceeds 4 mol%, the strength is significantly reduced. The yttria concentration suitable for high intensity is 2.5 to 3 mol%, and the yttria concentration suitable for total light transmittance is 3 to 4 mol%.

  The translucent zirconia sintered body of the present invention further contains 0.1 to 0.2 wt% of alumina as an additive. If the additive is less than 0.1 wt%, the sintering speed is slow, so the relative density does not reach 99.8% and the translucency is poor. If it exceeds 0.2 wt%, the sintering speed becomes too fast, so that many pores are generated during sintering, the relative density does not reach 99.8%, and the translucency is poor. A more preferable addition amount of alumina is 0.12 to 0.18 wt%.

  The translucent zirconia sintered body of the present invention satisfies the above composition and has a relative density of 99.8% or more, so that the total light transmittance at a thickness of 1.0 mm satisfies 35% or more. To do.

  The translucent zirconia sintered body of the present invention is obtained by atmospheric pressure sintering without using pressure sintering such as HIP, and has a total light transmittance of at least 35% or more at a thickness of 1.0 mm. Preferably, it has a high translucency up to 37% and further up to 40%.

  The translucent zirconia sintered body of the present invention preferably further has a crystal grain size of 0.20 to 0.45 μm. When the crystal grain size is less than 0.20 μm, there are many fine pores between and within the grains, so that the relative density does not reach 99.8%. If the crystal grain size exceeds 0.45 μm, the hydrothermal deterioration of the sintered body proceeds remarkably and the sintered body is destroyed, which is not suitable.

  The translucent zirconia sintered body of the present invention preferably has a monoclinic phase ratio of 20 to 30% after being immersed in hot water at 140 ° C. for 24 hours. When the monoclinic phase ratio exceeds 30%, the hydrothermal deterioration of the sintered body proceeds remarkably, and the sintered body is destroyed.

  The translucent zirconia sintered body of the present invention preferably has a three-point bending strength of 1200 MPa or more. The three-point bending strength is 1300 MPa or more, and more preferably 1400 MPa or more.

  The zirconia powder for a translucent zirconia sintered body of the present invention comprises 2 to 4 mol% of yttria as a stabilizer and 0.1 to 0.2 wt% of alumina having a particle diameter of 0.01 to 0.5 µm as an additive. In particular, those containing 0.1 to 0.2 wt% of alumina sol having a particle size of 0.01 to 0.05 μm are preferable.

The zirconia powder for a translucent zirconia sintered body of the present invention preferably has a BET specific surface area in the range of 5 to 15 m ² / g. When the BET specific surface area of the zirconia powder is smaller than 5 m ² / g, the powder is difficult to sinter on the low temperature side, and when it is larger than 15 m ² / g, the cohesive force between the particles becomes remarkable. A more preferable BET specific surface area is 5 to 10 m ² / g, and further 6 to 9 m ² / g.

  The zirconia powder for a translucent zirconia sintered body of the present invention preferably has an average particle diameter in the range of 0.3 to 0.7 μm. When the average particle size of the zirconia powder is smaller than 0.3 μm, the number of fine particles that increase the cohesiveness of the powder increases and it becomes difficult to mold. On the other hand, when the average particle size is larger than 0.7 μm, there are many coarse particles containing hard agglomerated particles. Therefore, it becomes difficult to mold, and the coarse particles inhibit the densification of the sintering, so that the sinterability is poor. A preferable average particle diameter is 0.4 to 0.5 μm.

  The zirconia powder for a translucent zirconia sintered body of the present invention may be obtained by drying, calcining and pulverizing, for example, a hydrated zirconia sol obtained by hydrolysis of a zirconium salt aqueous solution. After adding alkali metal hydroxide and / or alkaline earth metal hydroxide to hydrated zirconia sol obtained by hydrolysis until the reaction rate becomes 98% or more, yttrium as a raw material for the stabilizer It is preferable to add and dry.

  Zirconium salts used for the production of the hydrated zirconia sol include zirconium oxychloride, zirconyl nitrate, zirconium chloride, zirconium sulfate, etc. In addition to this, 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.

  The dried powder of hydrated zirconia sol obtained above is calcined at a temperature of 1000 to 1250 ° C. If the calcining 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 0.00 because the number of coarse particles containing hard agglomerated particles increases. Outside the range of 3 to 0.7 μm, the zirconia powder of the present invention cannot be obtained. A more preferable calcining temperature is 1050 to 1150 ° C.

  Next, the sinterability of the present invention is further improved by wet-grinding the calcined powder obtained above using a zirconia ball having a diameter of 3 mm or less until the average particle diameter is in the range of 0.3 to 0.7 μm. It is preferable to adjust to the range.

  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.

  Examples of the aluminum raw material compound used in the zirconia powder for the light-transmitting zirconia sintered body of the present invention include alumina, hydrated alumina, alumina sol, aluminum hydroxide, aluminum chloride, aluminum nitrate, and aluminum sulfate. be able to.

As the alumina sol, particularly when using an alumina sol having an average particle size of 0.01 to 0.05 μm and a BET specific surface area of 30 to 150 m ² / g, and further an alumina sol having a BET specific surface area of 30 to 290 m ² / g, By mixing and sintering with zirconia powder, a highly translucent zirconia sintered body is obtained.

On the other hand, as the alumina, α-alumina having an average particle diameter of 0.05 to 0.5 μm and a BET specific surface area of 5 to 50 m ² / g can be used.

The zirconia powder for a translucent zirconia sintered body of the present invention has a sintering shrinkage rate (Δρ /) at a relative density of 70% to 90% in atmospheric pressure sintering (in the atmosphere, a heating rate of 300 ° C./hour). (ΔT: g / cm ³ · ° C.) is preferably 0.0125 or more and 0.0160 or less (the relative density in the composition of the present invention is calculated by the theoretical density obtained by the formula of Formula 2). .

  The zirconia powder for a translucent zirconia sintered body of the present invention is formed into a molded body having a relative density of about 50 ± 5% by ordinary press molding (hydrostatic pressure pressing (CIP treatment if necessary)). When such a molded body is heated in the atmosphere, sintering shrinkage starts from a temperature equal to or higher than the calcination temperature, particularly around 1100 ° C. The shrinkage rate of sintering is constant in the range from 70% to 90% relative density. The shrinkage rate gradually decreases from the point where the relative density exceeds 90%, and finally the temperature is further increased near 100%. But it will not shrink.

The sintering shrinkage rate (Δρ / ΔT: g / cm ³ · ° C.) from 70% to 90% relative density in atmospheric pressure sintering (in the air, heating rate 300 ° C./hour) is obtained by molding zirconia powder. (After die molding, CIP treatment (pressure 2 t / cm ² )), and then can be measured by a general-purpose thermal dilatometer (DL9700 manufactured by ULVAC-RIKO). Since the sintering shrinkage rate in the present invention is a measured value at a relative density of 70% or more, it is not affected by variations in the initial molding density (relative density around 50%). Furthermore, since the sintering shrinkage rate is constant at a relative density of 70% to 90%, and the shrinkage rate is a linear function of temperature and relative density, an accurate shrinkage rate can be easily obtained without using a special approximate calculation process. It is possible to ask.

The zirconia powder for a translucent zirconia sintered body of the present invention has a sintering shrinkage rate (Δρ /) at a relative density of 70% to 90% in atmospheric pressure sintering (in the atmosphere, a heating rate of 300 ° C./hour). If ΔT: g / cm ³ · ° C.) deviates from the above range, it is difficult to obtain a sintered body having a high translucency with a relative density of 99.8% or more.

The zirconia powder of the present invention is one that can obtain a highly translucent sintered body in normal pressure sintering without using pressure sintering such as HIP treatment. It is preferable to have specific sinterability (sintering shrinkage rate) with respect to the physical properties of The higher the sintering shrinkage rate (Δρ / ΔT: g / cm ³ · ° C.) referred to in the present invention, the better. When the sintering shrinkage rate deviates from the scope of the present invention with respect to the physical properties of alumina, it is difficult to obtain a sintered body having high translucency in atmospheric pressure sintering.
The sintering shrinkage rate used in the present invention is different when the heating rate changes, but has a constant value when the heating rate is determined, and is a value inherent to the powder.

In the powder of the present invention, when the average particle size of alumina used is 0.01 μm or more and less than 0.05 μm, the sintering shrinkage rate (Δρ / ΔT: g / cm ³ · ° C.) is 0.0125 or more and 0.0135 or less. If it is out of this range, a zirconia sintered body having high translucency cannot be obtained in normal pressure sintering, particularly 1450 ° C. or lower, and even in normal pressure sintering at 1400 ° C. or lower.

In the powder of the present invention, when the average particle diameter of alumina used is more than 0.05 μm and 0.5 μm or less, the sintering shrinkage rate (Δρ / ΔT: g / cm ³ · ° C.) exceeds 0.0135 and is 0.00. 0160 or less. If it exceeds 0.0160, a sintered body with high translucency cannot be obtained in normal pressure sintering, particularly 1450 ° C. or lower, and further, 1400 ° C. or lower. On the other hand, when an alumina having an average particle size of more than 0.05 μm and 0.5 μm or less is used in the composition of the present invention, it is difficult to prepare one having a sintering shrinkage rate of less than 0.0135.

  The zirconia powder for a translucent zirconia sintered body of the present invention is preferably a spray-molded powder granule, and in particular, a spray granulated powder containing an organic binder in addition to yttria as a stabilizer and alumina sol as an additive. Is preferably used.

When zirconia granules are formed by spray drying with zirconia powder as a slurry, the flowability when forming a molded body is high, and bubbles are hardly generated in the sintered body. It is preferable that the granule has a particle size of 30 to 80 μm and a light bulk density of 1.10 to 1.40 g / cm ³ .

  In the case of using a binder for the granule, examples of the binder include commonly used binders such as polyvinyl alcohol, polyvinyl butyrate, wax, and acrylic. Among them, carboxyl groups or derivatives thereof (for example, salts, Acrylic materials having an ammonium salt are particularly preferred. Examples of the acrylic binder include polyacrylic acid, polymethacrylic acid, acrylic acid copolymer, methacrylic acid copolymer, and derivatives thereof. The amount of the binder added is preferably 0.5 to 10% by weight, particularly 1 to 5% by weight, based on the ceramic powder in the ceramic powder slurry.

  The translucent zirconia sintered body of the present invention is a zirconia powder containing 2 to 4 mol% of yttria as a stabilizer and 0.1 to 0.2 wt% of alumina sol having a particle diameter of 0.01 to 0.05 μm as an additive. After being molded, it is preferably produced by sintering at 1350 to 1450 ° C., particularly 1400 ° C. or less and 100 ° C./hour or less under normal pressure.

  When the sintering temperature is less than 1350 ° C., the relative density does not reach 99.8%, and when it exceeds 1450 ° C., the hydrothermal degradation of the sintered body proceeds remarkably, and the sintered body tends to break.

  The translucent zirconia sintered body of the present invention is obtained by atmospheric pressure sintering, but the sintering atmosphere is not particularly limited as long as it is not a reducing atmosphere, and may be an oxygen atmosphere or in-air sintering. It is particularly preferable to sinter in the atmosphere.

  Since the translucent zirconia sintered body of the present invention has high density, high strength and excellent translucency, the zirconia sintered body used in dental applications, specifically, a mill blank such as a denture material, It is excellent as a sintered body used as an orthodontic bracket, and the powder for a translucent zirconia sintered body of the present invention can be sintered under normal pressure without using a large pressure sintering apparatus such as HIP. A translucent zirconia sintered body can be manufactured.

  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 diameter of the zirconia powder was measured using a Microtrac particle size distribution meter (manufactured by Honeywell, model: 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, model: 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 pressure of 700 kgf / cm ² , and the preform was subjected to cold isostatic pressing (CIP) treatment at a pressure of 2 t / cm ² using a rubber mold to obtain a molded body. The obtained molded body was sintered at a predetermined temperature (holding time 2 hours). The average particle diameter of the crystal grains of the zirconia sintered body is determined by subjecting the mirror-polished sintered body to a thermal etching treatment and using a field emission scanning electron microscope (FESEM) (manufactured by JEOL Ltd., model: JSM-T220). Calculated by the planimetric method. The sintered body density was measured by Archimedes method.

  The total light transmittance of the sintered body was measured with a light source D65 in accordance with JIS K7361 using a turbidimeter (Nippon Denshoku Industries Co., Ltd., model: NDH2000). The sample used was a disc-shaped one having a thickness of 1 mm obtained by polishing the sintered body on both sides. The strength of the sintered body was evaluated by a three-point bending measurement method.

  The hydrothermal durability test was evaluated by immersing the sintered body in 140 ° C. hot water for 24 hours and determining the ratio of the monoclinic phase to be formed (monoclinic phase ratio). The monoclinic phase ratio was obtained by the above-described Equation 1 by the same calculation method as that of the monoclinic phase ratio of the zirconia powder after XRD measurement was performed on the sintered sintered body.

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%. Distilled water was added to the hydrated zirconia sol 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 1140 ° C. for 2 hours. The obtained calcined powder was washed with water, and then an alumina sol having a particle size of 0.015 μm was added to a slurry having an alumina content of 0.10 wt% and distilled water to give a zirconia concentration of 45 wt%. This slurry was treated with a vibration mill for 24 hours using zirconia balls having a diameter of 2 mm to obtain zirconia powder.

Table 1 shows the Al ₂ O ₃ content, the BET specific surface area, the average particle diameter, and the monoclinic phase rate of the obtained zirconia powder. The obtained zirconia powder 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 the slurry, spray granulation was performed. The obtained zirconia granules had an average particle size of 50 μm and a light bulk density of 1.21 g / cm ³ .

Next, the zirconia granules obtained above were press-molded with CIP (pressure 2 t / cm ² ) and sintered under the condition of 1450 ° C. Table 2 shows the sintering temperature, sintered body density, bending strength, crystal grain size, and monoclinic crystal phase rate after the hydrothermal durability test of the obtained sintered body.

  The total light transmittance was 37%, and it was confirmed that the sintered body was excellent in translucency. Further, the monoclinic phase ratio after the hydrothermal durability test was 21%, and it was confirmed that the sintered body was not easily deteriorated.

Example 2
A zirconia powder was obtained in the same manner as in Example 1 except that 0.12% by weight of alumina sol was added in terms of alumina content. The properties of the obtained zirconia powder are shown in Table 1. Thereafter, the obtained zirconia powder is dispersed in water to obtain a zirconia slurry having a slurry concentration of 50%, and an acrylic binder and polyvinyl alcohol are added to this slurry in an amount of 3 wt% with respect to the zirconia in the zirconia slurry. Was added to adjust the viscosity, and then spray granulation was performed to produce zirconia granules. The obtained zirconia granules had an average particle size of 45 μm and a light bulk density of 1.20 g / cm ³ .

Subsequently, the zirconia granule fine powder obtained above was press-molded with CIP (pressure 2 t / cm ² ) and sintered under the condition of 1450 ° C.

  Table 2 shows the sintering temperature, sintered body density, bending strength, crystal grain size, and monoclinic crystal phase rate after the hydrothermal durability test of the obtained sintered body. The total light transmittance was 35%, and it was confirmed that the sintered body was excellent in translucency. Further, the monoclinic phase rate after the deterioration test was 20%, and it was confirmed that the sintered body was not easily deteriorated.

Example 3
A zirconia fine powder was obtained under the same conditions as in Example 1 except that the alumina sol was added so that the alumina content was 0.17 wt%. The characteristics of the obtained zirconia fine powder are shown in Table 1. Using the zirconia fine powder, zirconia granules were obtained in the same manner as in Example 2. The obtained zirconia granules had an average particle size of 40 μm and a light bulk density of 1.18 g / cm ³ .

  Next, the zirconia granules obtained above were press-molded and sintered under the condition of 1400 ° C. Table 2 shows the sintering temperature, sintered body density, bending strength, crystal grain size, and monoclinic crystal phase rate after the deterioration test of the obtained sintered body. The total light transmittance was 39%, and it was confirmed that the sintered body was excellent in translucency. Further, the monoclinic phase ratio after the deterioration test was 28%, and it was confirmed that the sintered body was not easily deteriorated.

Example 4
A zirconia sintered body was obtained in the same manner as in Example 3 except that the sintering temperature of the zirconia granules was 1350 ° C. However, at the time of sintering, the place where the temperature was normally raised at 100 ° C./hour was sintered at a low temperature raising rate of 50 ° C./hour.

  Table 2 shows the sintering temperature, sintered body density, bending strength, crystal grain size, and monoclinic crystal phase rate after the hydrothermal durability test of the obtained sintered body. The total light transmittance was 38%, and it was confirmed that the sintered body was excellent in translucency. Further, the monoclinic phase rate after the deterioration test was 5%, and it was confirmed that the sintered body was not easily deteriorated.

Example 5
A zirconia powder was obtained in the same manner as in Example 3 except that the calcining temperature during production of the zirconia powder was 1220 ° C. The characteristics of the obtained zirconia fine powder are shown in Table 1.

Using the zirconia fine powder, zirconia granules were obtained in the same manner as in Example 2. The obtained zirconia granules had an average particle size of 40 μm and a light bulk density of 1.12 g / cm ³ .

  Next, the zirconia granules obtained above were press-molded and sintered under the condition of 1400 ° C. However, at the time of sintering, the place where the temperature was normally raised at 100 ° C./hour was sintered at a low temperature raising rate of 50 ° C./hour. Table 2 shows the sintering temperature, sintered body density, bending strength, crystal grain size, and monoclinic crystal phase rate after the hydrothermal durability test of the obtained sintered body. The total light transmittance was 39%, and it was confirmed that the sintered body was excellent in translucency. Further, the monoclinic phase ratio after the hydrothermal durability test was 27%, and it was confirmed that the sintered body was hardly deteriorated.

Example 6
A zirconia powder was obtained in the same manner as in Example 3 except that the calcining temperature during production of the zirconia powder was 1080 ° C. The properties of the obtained zirconia powder are shown in Table 1.

Using the zirconia powder, zirconia granules were obtained in the same manner as in Example 2. The obtained zirconia granules had an average particle size of 42 μm and a light bulk density of 1.23 g / cm ³ .

  Next, the zirconia granules obtained above were press-molded and sintered under the condition of 1400 ° C. However, at the time of sintering, the place where the temperature was normally raised at 100 ° C./hour was sintered at a low temperature raising rate of 50 ° C./hour. Table 2 shows the sintering temperature, sintered body density, bending strength, crystal grain size, and monoclinic crystal phase rate after the hydrothermal durability test of the obtained sintered body. The total light transmittance was 38%, and it was confirmed that the sintered body was excellent in translucency. Further, the monoclinic phase ratio after the hydrothermal durability test was 29%, and it was confirmed that the sintered body was hardly deteriorated.

Comparative Example 1
A zirconia powder was obtained in the same manner as in Example 1 except that the alumina sol was added in an alumina content of 0.075% by weight. Using the zirconia powder, zirconia granules were obtained in the same manner as in Example 1. The characteristics of the obtained zirconia fine powder are shown in Table 1.

Next, the zirconia granules obtained above were press-molded with CIP (pressure 2 t / cm ² ) and sintered under the condition of 1450 ° C. Table 2 shows the sintering temperature, sintered body density, bending strength, crystal grain size, and monoclinic crystal phase rate after the hydrothermal durability test of the obtained sintered body. The monoclinic phase ratio after the hydrothermal durability test was 10%, and it was confirmed that the sintered body was not easily deteriorated. However, the total light transmittance was as low as 29%, and the sintered body was poor in translucency. It turns out that.

Comparative Example 2
A zirconia powder was obtained under the same conditions as in Example 1 except that the alumina content in Example 1 was 0.25 wt% with alumina powder and the pulverization time was 8 hours. Zirconia granules were obtained in the same manner as in No. 2. The properties of the obtained zirconia powder are shown in Table 1.

Next, the zirconia granules obtained above were press-molded with CIP (pressure 2 t / cm ² ) and sintered at 1500 ° C. Table 2 shows the sintering temperature, sintered body density, bending strength, crystal grain size, and monoclinic crystal phase rate after the hydrothermal durability test of the obtained sintered body. The monoclinic phase ratio after the hydrothermal durability test was 50%, and it was confirmed that the sintered body is easily deteriorated and has low reliability. Moreover, it turned out that it is a sintered compact with a total light transmittance as low as 32%, and poor in translucency.

Comparative Example 3
A zirconia powder was obtained under the same conditions as in Example 1 except that the calcining temperature of Example 1 was 900 ° C., alumina content was 0.25 wt% with alumina powder, and treatment was performed with a vibration mill for 8 hours. Was used to obtain zirconia granules in the same manner as in Example 2.

  The properties of the obtained zirconia powder are shown in Table 1.

  Next, the zirconia granules obtained above were press-molded and sintered under the condition of 1350 ° C. Table 2 shows the sintering temperature, sintered body density, bending strength, crystal grain size, and monoclinic crystal phase rate after the hydrothermal durability test of the obtained sintered body.

  Although the monoclinic phase ratio after the hydrothermal durability test was 5%, it was confirmed that the sintered body was not easily deteriorated. However, it was found that the sintered body had a very low total light transmittance of 18%. It was.

Examples 7-10, Comparative Examples 4-7
To the hydrated zirconia sol obtained by the hydrolysis reaction, yttrium chloride was added so that the yttria concentration was 3 mol%, and after drying, the same alumina sol as used in Examples 1 to 6 and the average particle size were Using 0.3 μm α-alumina powder, a zirconia powder having a BET surface area of 10 to 15 m ² / g was prepared.

The obtained powder was press-molded with CIP (pressure 2 t / cm ² ) and sintered under the condition of 1400 ° C. Similarly, a CIP-molded compact was subjected to a sintering shrinkage rate (Δρ /) from a relative density of 70% to 90% at a heating rate of 300 ° C./hour in the atmosphere using a heat shrinkage meter (DL9700 manufactured by ULVAC-RIKO). ΔT: g / cm ³ · ° C.).

Al ₂ O ₃ content (particle size) of zirconia powder, BET specific surface area, sintering shrinkage rate with relative density from 70% to 90% (Δρ / ΔT: g / cm ³ · ° C.), and normal in air Table 3 shows the sintering density when sintering was performed at a pressure of 1400 ° C. and a heating rate of 100 ° C./hour.

  When the average particle size of alumina is 0.01 μm or more and less than 0.05 μm, it is 0.0125 or more and 0.0135 or less. When the average particle size of alumina is more than 0.05 μm and 0.5 μm or less, 0.0135 And a translucent zirconia sintered body having a relative density of 99.8% or more was obtained at a temperature exceeding 0.0160 and below.

The relationship between the sintering shrinkage rate (Δρ / ΔT: g / cm ³ · ° C.) and the sintered body relative density is shown in FIG.

  When the alumina content is 0.1 to 0.2 wt%, transmissivity with a total light transmittance of 35% or more is obtained only in a sintered body having a relative density of 99.8% or more, and the transmittance is 35% or more. To achieve this, a relative density of 99.8% or more is essential.

Relationship between sintering shrinkage rate (Δρ / ΔT: g / cm ³ · ° C.) and sintered body relative density Example of heat shrinkage curve in atmospheric pressure sintering of zirconia powder (temperature increase rate: 300 ° C./hour) (Example 7)

Claims (5)

A powder for translucent zirconia sintered body containing 2 to 4 mol% of yttria as a stabilizer and 0.1 to 0.2 wt% of alumina having a particle diameter of 0.01 to 0.5 µm as an additive. The powder according to claim 1, wherein the BET specific surface area is 5 to 15 m ² / g and the average particle size is 0.3 to 0.7 μm. Sintering shrinkage rate (Δρ / Δ) of alumina having an average particle size of 0.01 μm or more and 0.5 μm or less and a relative density of 70% to 90% in atmospheric pressure sintering (in the atmosphere, temperature rising rate 300 ° C./hour) ^3. The powder according to claim 1, wherein T: g / cm ³ · ° C.) is 0.0125 or more and 0.0160 or less. The average particle diameter of alumina is 0.01 μm or more and 0.05 μm or less, and the sintering shrinkage rate (Δρ / Δ) from 70% to 90% relative density in atmospheric pressure sintering (in the atmosphere, the heating rate is 300 ° C./hour). The powder according to any one of claims 1 to ³ , wherein T: g / cm ³ · ° C) is 0.0125 or more and 0.0135 or less. The average particle size of alumina is more than 0.05 μm and 0.5 μm or less, and the sintering shrinkage rate (Δρ / The powder according to any one of claims 1 to ³ , wherein ΔT: g / cm ³ · ° C) is more than 0.0135 and not more than 0.0160.

Images