JPH0225864B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for manufacturing a zirconia sintered body with excellent translucency. [Conventional technology] Conventionally, ZrO ₂ was used as a translucent zirconia sintered body.
-Y ₂ O ₃ system and ZrO ₂ -CaO system two-component sintered bodies are respectively published in the Journal of the American
Ceramic Society (Journal of The
American Ceramic Society, Vol. 50, p. 532 (1967) and Journal of Less-Common Metals.
Metals), Vol. 13, p. 530 (1967), the light transmittance of these sintered bodies is approximately 10
%, and it cannot be said that it is a truly translucent material. [Problems to be Solved by the Invention] The present invention provides a method for manufacturing a zirconia sintered body having extremely high translucency and which can be used as an optical material. [Means for solving the problem] Generally, in order to impart translucency to ceramics, it is necessary to increase the density of the sintered body to reduce light scattering by pores, and to increase the particle size of the sintered body. It is said that reducing light scattering due to grain boundaries is effective. As a result of conducting research on ZrO ₂ −Y ₂ O ₃ based sintered bodies, the present inventor discovered that ZrO ₂ −Y ₂ O ₃
We have found that grain growth in sintered bodies is significantly promoted by adding TiO ₂ to the system. However, in general, significant grain growth results in pores remaining within the grains because the growth rate of the grains is faster than the movement of pores, making it difficult to obtain a dense sintered body. In order to overcome this drawback, the present inventor investigated the characteristics of the raw material powder and the sintering conditions, and found that a system in which TiO ₂ was added to the ZrO ₂ -Y ₂ O ₃ system had remarkable grain growth and complete densification. The inventors have discovered that this can be achieved without producing contradictory results, and have succeeded in obtaining a zirconia sintered body with high translucency. In the present invention, a molded body consisting of 2 mol % or more of Y ₂ O ₃ , 3 to 20 mol % of TiO ₂ , and the remainder ZrO ₂ is fired in an oxygen-containing atmosphere, subjected to hot isostatic treatment, and then heated in air or oxygen. A method for producing a translucent zirconia sintered body by oxidation treatment is provided. manufactured in this way
A sintered body containing 3 to 20 mol% of TiO ₂ has a tetragonal single phase at around 2 mol% of Y ₂ O ₃ , and a cubic single phase at 6 mol % or more of Y ₂ O ₃ , with tetragonal and cubic crystals in between. It becomes a mixed crystal with crystal. A sintered body consisting of a cubic single phase is optically isotropic, so there is no scattering due to grain boundaries.
It exhibits extremely high translucency. However, Y ₂ O ₃ is 9
It is not necessary to contain more than mol%. _TiO2
As the amount added increases, the grain size of the sintered body increases.
For example, if sintering is performed at 1700℃ for 2 hours,
For 5 mol% _TiO2, the particle size is 50 to 100 μm, and for 10 mol% _TiO2, the particle size is 100 to 200 μm. Light transmittance tends to increase as the particle size increases. However, when the TiO ₂ content exceeds 20 mol %, another compound ZrTiO ₄ is formed as a second phase, resulting in a significant decrease in light transmittance. Therefore, in order to obtain sufficiently high translucency, the TiO ₂ content should be 3 to 3.
It should be 20 mol%, preferably 5 to 20 mol%. The present inventor has determined that Y ₂ O ₃ is 6 mol% or more and TiO ₂ is 3 mol % or more.
In addition to ~20 mol%, the zirconia sintered body contains a small amount of lanthanum-based rare earth oxide, which is transparent and has
It was discovered that it also has fluorescent properties. The content of the lanthanum-based rare earth oxide is desirably 0.1 to 3 mol %, and is preferably around 1 mol % in order to exhibit good fluorescence emission. In addition, examples of lanthanum-based rare earth oxides include Nd ₂ O ₃ , Eu ₂ O ₃ ,
Examples include Tb ₂ O ₃ and the like. The method for manufacturing the sintered body of the present invention will be explained in detail below. The starting material is preferably a high purity fine powder. For example, a powder obtained by sufficiently mixing a ZrO ₂ -Y ₂ O ₃ type fine powder with an average particle size of 0.1 μm or less and a TiO ₂ fine powder with an average particle size of 0.5 μm or less synthesized by a wet method may be used, but ZrO It is even more preferable to mix _{the 2} -Y ₂ O ₃ powder and the TiO ₂ powder sufficiently, sinter it, and grind it to an average particle size of 0.3 μm or less, in which the components are dissolved into solid solution with each other. Or average particle size 0.3μm synthesized by coprecipitation method
The following ZrO ₂ −Y ₂ O ₃ −TiO ₂ type fine powder and ZrO ₂ −
A suitable raw material is one obtained by mixing a titanium alkoxide solution with a Y ₂ O ₃ powder, drying, calcining, and pulverizing the powder with an average particle size of 0.3 μm or less. The lanthanum-based rare earth oxide may be added by mixing oxalate or the like into the ZrO ₂ -Y ₂ O ₃ -TiO ₂ -based powder precursor before calcination, and then firing the mixture. After molding such powder into a predetermined shape using a molding method such as rubber press or slip cast method,
Fire. The firing temperature may be 1400°C or higher, preferably 1600 to 1800°C to achieve sufficient grain growth. Further, the temperature increase rate is preferably 100° C./hr or less. The firing atmosphere may be air, but in order to obtain even higher translucency, it is preferable to use oxygen. The sintered body thus obtained already has high translucency, but in order to make it even more translucent, it is then placed in a hot isostatic press and processed. As the processing conditions, it is preferable to select a pressure medium of argon, a pressure of 500 atmospheres or more, and a temperature of 1400 to 1700°C. This treatment brings the sintered body into a reduced state, so that it becomes black. Therefore, it is necessary to oxidize this black sintered body in air or oxygen to return it to its original color. The processing temperature is 800℃ or higher, preferably
The temperature is 1000℃ or higher, and 1200℃ is sufficient. The sintered body thus obtained has a theoretical value of 99
% or more, and exhibits high transparency to light in the visible to infrared wavelength range of 350 to 7000 nm. Furthermore, when irradiated with ultraviolet rays, those containing lanthanum-based rare earth oxides emit red fluorescence, for example those containing Eu ₂ O ₃ and green fluorescence when containing Tb ₂ O ₃ . [Effects of the Invention] The sintered body obtained by the present invention has excellent translucency and a high refractive index, and also has the advantage that large products and products with complicated shapes can be easily manufactured. have Furthermore, it can be used as a transparent body having fluorescence emission by containing a lanthanum-based rare earth oxide. Therefore, light transmitting materials that require heat resistance and heat insulation, such as windows of furnace bodies, cladding tubes of heating elements, and protection tubes of lamps; infrared transmitting materials such as infrared lenses, windows of infrared light-receiving elements; It can be used for industrial applications such as fluorescent display materials, solid-state oscillation materials, and ultraviolet dosimeters; decorative materials for watches, jewelry, etc. [Example] The present invention will be explained using an example. Powder production examples 1 to 3 A mixed aqueous solution of zirconium oxychloride and yttrium chloride is hydrolyzed by boiling, and the resulting sol is dried, calcined at 900°C, and pulverized to produce Y ₂ O ₃ A fine zirconia powder containing . This powder and titanium isopropoxide solution were placed in ethanol, mixed wet, dried under reduced pressure, fired at 950°C, and then ground to form ZrO ₂ −
A Y ₂ O ₃ −TiO ₂ based fine powder was obtained. Powder Production Examples 4 to 6 Zirconia fine powder containing Y ₂ O ₃ and titania fine powder obtained in the same manner as in Powder Production Examples 1 to 3 were wet mixed in ethanol, dried,
It was calcined at _℃ and pulverized to obtain _ZrO2 - _Y2O3 - _TiO2- based fine powder. Powder production example 7 A titanium isopropoxide solution was added to a mixed aqueous solution of zirconium oxychloride and yttrium chloride, and the mixture was hydrolyzed by continuing heating for 3 days. After drying the resulting sol, it was calcined at 920°C. A ZrO ₂ -Y ₂ O ₃ -TiO ₂ -based fine powder was obtained by pulverization. Powder Production Examples 8-13 Zirconia powder was obtained in the same manner as in Powder Production Examples 1-3. Additionally, water was added to the titanium isopropoxide solution to obtain a hydrolysis product of hydrated titania. The above zirconia powder and the hydrolysis product of hydrated titania were wet mixed, dried, and heated to 1000°C.
The mixture was fired for 2 hours and pulverized to obtain ZrO ₂ -Y ₂ O ₃ -TiO ₂ -based fine powder. Powder Production Examples 14-18 Neodymium oxalate was added to a mixture of zirconia powder and hydrated titania hydrolysis product obtained in the same manner as in Powder Production Examples 8-13, wet-pulverized, and dried. It was baked at ℃ for 1 hour. The obtained calcined powder was crushed to form a solid solution of Nd ₂ O ₃ .
A ZrO ₂ −Y ₂ O ₃ −TiO ₂ based fine powder was obtained. The composition and primary particle size of the above fine powder are shown in Table 1.
It is as follows. Sintering Example A The powders obtained in Powder Production Examples 1 to 7 were molded into a disk shape using a mold and a rubber press. These molded bodies were placed in a tube furnace, and the temperature was raised at a rate of 40° C./hr while oxygen was being passed through, and the temperature was maintained at 1700° C. for 2 hours, and then the temperature was lowered. The sintered body thus obtained is placed in a hot isostatic press,
30 at 1000 atm and 1500℃ with argon as pressure medium
It was processed separately. All of the sintered bodies after the treatment had a black color, so they were put into the tube furnace again and kept at 1200°C for 4 hours while flowing oxygen. After cooling, all of the sintered bodies taken out had very high translucency. When the crystal phase was identified by X-ray diffraction, it was found that the sintered body obtained from Powder Production Example 4 had a single tetragonal phase, but all the rest had a single cubic phase. Test Example A Some of the sintered bodies obtained in Sintering Example A were selected and their light transmittance was measured. Thickness as measurement sample
A mirror-polished piece on both sides with a thickness in the range of 0.5 to 1.5 mm was used. The results are shown in Figure 1. Codes 1 and 2 in the diagram
and 3, the raw material powder is powder production example 2,
5 and 3. From FIG. 1, it can be seen that the sintered body of the present invention has a transmittance in the visible light range of 40% or more at a thickness of 1 mm. Test Example A′ For the purpose of examining the effect of TiO ₂ , powder containing TiO ₂ (Production Example 2) and powder containing no TiO ₂ (8 mol%
A disk-shaped sintered body with a thickness of 1 mm was obtained using the same method as in Sintering Example A using Y ₂ O ₃ -containing zirconia). The TiO ₂ -containing sample had very high light transmittance, while the TiO ₂ -free sample had a white color. When the transmittance in the visible light range was measured by the method of Test Example 1, the former was about 40%, but the latter was about 7%. The structures of the sintered bodies of these two samples were observed using a scanning electron microscope. Figure 2 is a micrograph of the same, where A is the one containing TiO ₂ and B is the one without TiO 2 . As is clear from Figure 2, the particle size has become approximately 200 μm due to the addition of TiO ₂ .
Significant grain growth is achieved and porosity is greatly reduced. This result proves that TiO ₂ addition plays an important role in enhancing the transparency. Sintering Example B The powders obtained in Powder Production Examples 8 to 13 were molded into a plate shape using a mold and a rubber press. These molded bodies are placed in a tube furnace, and the temperature is increased while oxygen is flowing.
The temperature was raised at a rate of 50°C/hr and held at 1500-1750°C for 2 hours, and then the temperature was lowered. All of the obtained sintered bodies had high translucency. Next, these sintered bodies were cut in half, and the pieces were placed in a hot isostatic press (HIP) device and treated at 1,000 atmospheres and 1,500 to 1,700°C for 30 minutes using argon as a pressure medium. All of the sintered bodies after the treatment had a black color, so they were placed in the tube furnace again and held at 1200°C for 2 hours while flowing oxygen. After cooling, all of the sintered bodies taken out had very high translucency.
The crystal phase of the obtained sintered bodies was cubic. The particle size and density are shown in Table 2. Test Example B The light transmittance of the sintered body obtained in Sintering Example B to visible light and infrared light was measured. Thickness as measurement sample
A 0.8 mm mirror-polished piece was used on both sides. All samples exhibited transparency to light with wavelengths ranging from 0.35 to 7 μm, visible light to infrared light. As a representative value,
Table 2 shows the linear transmittance for 0.6 μm light. Sintering Example C A sintered body was obtained in the same manner as Sintering Example B using the zirconia powders obtained in Powder Production Examples 14 to 18.
The crystal phase of the obtained sintered bodies was cubic. The particle size and density are shown in Table 3. Test Example C The light transmittance of visible light and infrared light of the sintered body obtained in Sintering Example C was measured. Thickness as measurement sample
A 0.8 mm mirror-polished piece was used on both sides. All samples exhibited transparency to light with wavelengths ranging from 0.35 to 7 μm, visible light to infrared light. Figure 3 shows the visible light transmittance of sintered sample No. 14. In addition, when irradiated with 0.26 μm ultraviolet rays, sintered sample No. 13 and
16 gave off a red glow, and 15 gave off a green glow.

【table】

【table】

【table】 [Brief explanation of drawings]

FIG. 1 is a graph showing the light transmittance in Test Example A. Figure 2 shows that in test example A',
It is a micrograph showing the grain structure of a sintered body. Third
The figure is a graph showing the visible light transmittance of sintered body sample No. 14 in Test Example C. The meanings of the symbols in the figure are as follows. 1: Raw material powder Powder production example 2, 2: Raw material powder
Powder production example 5, 3: Raw material powder Powder production example 3,
A: Sintered body containing _TiO2 , B: Sintered body not containing _TiO2 .

Claims (1)

[Claims] 1. A molded body consisting of 2 mol % or more of Y ₂ O ₃ , 3 to 20 mol % of TiO ₂ , and the remainder ZrO ₂ is fired in an oxygen-containing atmosphere, subjected to hot isostatic treatment, and then oxidized. A method for producing a translucent zirconia sintered body, characterized by: 2. The method according to claim 1, wherein the content of Y ₂ O ₃ in the molded body is 6 mol% or more. _3. The method according to claim 1, wherein the content of _Y2O3 in the molded body is 6 to 9 mol%, and the content of _TiO2 is 5 to 20 mol%. 4. The method according to claim 1, 2 or 3, wherein the molded body is fired at 1400°C or higher. 5. The method according to claim 4, wherein the molded body is fired at 1600 to 1800°C. 6. The method according to any one of claims 1 to 5, wherein the hot isostatic treatment is performed in an argon atmosphere at a pressure of 500 atmospheres or more at 1400 to 1700°C, and the oxidation treatment is performed at 800°C or more. 7 Y ₂ O ₃ 2 mol % or more, TiO ₂ 3 to 20 mol %, lanthanum rare earth oxide 0.1 to 3 mol %, and the remainder
A method for producing a translucent and luminescent zirconia sintered body, which comprises firing a ZrO ₂ molded body in an oxygen-containing atmosphere, subjecting it to hot isostatic treatment, and then subjecting it to oxidation treatment.