JP4458409B2 - Method for producing translucent ceramics and translucent ceramics - Google Patents

Description

  In the present invention, durability such as high pressure sodium lamp arc tube, high-temperature furnace window, infrared detection window material, heat-resistant lens, etc., durability at high temperatures (particularly 1000 ° C. or higher), ultraviolet / visible / infrared The present invention relates to a translucent aluminum magnesium oxynitride sintered body that is suitable as a material for parts that require high translucency with respect to light of a region wavelength.

In recent years, there has been an increasing demand for translucent materials that are excellent in translucency of light in the visible and infrared wavelengths, and that are also excellent in heat resistance and wear resistance. It is known that single-phase aluminum oxynitride can be obtained by adding aluminum nitride to alumina and sintering at high temperature (Patent Documents 1 and 2, Non-Patent Document 1). The crystal structure of aluminum oxynitride is an isotropic cubic structure. When this aluminum oxynitride is used, there is no light scattering due to birefringence at the grain boundary, and the oxynitride has a very high translucency. There is a possibility of obtaining an aluminum sintered body.
Japanese Patent Laid-Open No. 1-183472 JP-A-7-309667 "Effect of MgO addition on translucency of aluminum oxynitride spinel" (1996 issue: "Report on Yamaguchi Prefectural Industrial Technology Center" Masashi Hashimoto, Akira Mikuni)

  Up to now, as a method for producing a uniform sintered body of aluminum oxynitride, a raw material powder once having an aluminum oxynitride composition is produced, and this is hot-pressed in nitrogen or in vacuum, thereby translucent acid. A method for producing an aluminum nitride sintered body has been proposed. However, in this method, the manufacturing process is complicated and expensive.

  An object of the present invention is to obtain a translucent ceramic having a high translucency mainly composed of an aluminum oxynitride phase by atmospheric pressure sintering.

The present invention contains Al ₂ O ₃ and AlN at a molar ratio of 80 to 60%: 20 to 40%, and MgO powder having an average particle size of 0.6 to 1.2 μm is mixed with Al ₂ O ₃ and AlN. molding a mixed powder containing 2 to 10 parts by weight when the total amount was 100 parts by weight of the obtained molded body, and sintered the molded body at a maximum temperature of 1950-2050 ° C., to the maximum temperature It is maintained at a temperature of 1500 to 1750 ° C. at the time of temperature increase, and the rate of temperature increase from at least 1700 ° C. to the maximum temperature is 0.5 to 8 ° C./min. The present invention relates to a method for producing a photoceramic.

According to this method, a translucent ceramic having a high translucency mainly composed of an aluminum oxynitride phase can be obtained by atmospheric pressure sintering.
Of translucent ceramics, the most abundant phase needs to be an AlON phase. Preferably, in the X-ray diffraction measurement, when the total value of the peak intensity of the AlON phase and the peak intensity of the other crystal phase is 100%, the peak intensity of the other crystal phase is preferably 10% or less. % Or less is more preferable.

The proportions of Al ₂ O ₃ and AlN are 80 to 60% and 20 to 40% in terms of molar ratio. Thereby, an aluminum oxynitride phase can be generated as a main phase. When the total amount of Al ₂ O ₃ and AlN is 100 parts by weight, 2 to 10 parts by weight of MgO powder is added. By making the addition amount of MgO powder 2 parts by weight or more, the crystal particle diameter can be increased and the linear transmittance is improved. From this viewpoint, it is preferable that the added amount of the MgO powder is 2 parts by weight or more. Moreover, when the addition amount of MgO powder exceeds 10 weight part, many intragranular pores exist at the time of sintering and the translucency is inferior.

The average particle diameter of MgO powder shall be 0.6-1.2 micrometers. For example, in Non-Patent Document 1, the average particle diameter of MgO powder is as fine as 0.4 μm, but the change in linear transmittance is very large depending on the sintering temperature, and the characteristic variation due to the sintering temperature is large. By using MgO powder having a slightly larger average particle diameter as in the present invention, the Al ₂ O ₃ phase tends to remain in the final sintered body, and the change in linear transmittance due to the sintering temperature is small. A sintered body having a stable and high linear transmittance can be mass-produced.

  The maximum temperature during sintering of the molded body is 1950-2050 ° C. By setting the maximum temperature to 1950 ° C. or more and 2050 ° C. or less, the linear transmittance of the sintered body can be increased.

In the present invention, the rate of temperature increase from at least 1700 ° C. to the maximum temperature is 0.5-8 ° C./min in normal pressure sintering. In this way, by lowering the rate of temperature rise from the solid-phase reaction to sintering and slowing the reaction, while suppressing rapid densification, it diffuses intra-granular pores and grows crystal grains to increase translucency. Can be high. From this viewpoint, it is more preferable to set the rate of temperature rise at 1700 ° C. or higher to 2 ° C./min or lower.

The present invention also relates to a translucent ceramic obtained by the above method. This translucent ceramic preferably contains an Al ₂ O ₃ phase. Particularly preferably, the relative ratio of the peak heights of the AlON phase and the Al ₂ O ₃ phase is 95.0 to 99.5: 5.0 to 0.5 under the conditions described in the examples.

  Hereinafter, the manufacturing method of the translucent aluminum magnesium oxynitride sintered compact concerning this invention is demonstrated in detail. First, a mixed powder is prepared by mixing alumina powder, aluminum nitride powder and magnesium oxide powder at a predetermined blending ratio. The average particle size of the alumina powder is preferably 0.4 μm or less, and the average particle size of the aluminum nitride powder is preferably 0.6 μm or less. The average particle diameter of the magnesium oxide powder is 0.6 μm or more and 1.2 μm or less.

  The powder mixing method is not limited. For example, each powder is mixed in a ball mill in a solvent such as ethanol, and the obtained slurry is dried and prepared by a method such as spray drying, whereby a mixed powder having a good mixing state can be obtained.

  Next, the mixed powder is molded to obtain a molded body. This forming method is not limited. For example, uniaxial pressure molding using a mold and cold isostatic pressing (CIP) molding using a rubber mold can be exemplified. When mixed using a ball mill as described above, the slurry is poured directly into a porous mold such as gypsum, and after the mixed powder is placed in the mold, the molded product is released and dried. Can be obtained.

Then, the molded body is heated to a predetermined maximum temperature under atmospheric pressure or reduced pressure to cause solid phase reaction and sintering. At this time, by slowly raising the temperature to the maximum temperature, a solid phase reaction can be caused, and then sintering can be caused. By maintaining the temperature at a temperature lower than the maximum temperature for a certain period of time, the solid phase reaction of the alumina powder, the aluminum nitride powder and the magnesium oxide powder proceeds to produce an aluminum magnesium oxynitride (Mg—Al—O—N) phase. Can do. Thereafter, the temperature is raised from the holding temperature to the maximum temperature to cause sintering.

  The holding temperature is preferably in a temperature range of 1500 to 1750 ° C. When the holding temperature exceeds 1750 ° C., closed pores that cannot be removed by the subsequent treatment are likely to remain in the sintered body, which may reduce the translucency of the final product.

  An inert gas such as nitrogen gas, hydrogen gas, or argon can be used as the atmospheric gas during the solid phase reaction and sintering. Moreover, in order to prevent the reduction | restoration of the molded object during sintering, you may use the gas which mixed about 0.1-5% oxygen gas in the said nitrogen gas etc. or inert gas.

  When the solid-phase reaction of the molded body proceeds, the temperature is further raised to the maximum temperature to obtain a sintered body. The holding time at the maximum temperature is suitably 3 to 10 hours.

The sintered body of each example shown to T-1-13 of Table 1 was produced as follows.
(Powder) Specifically, Al ₂ O ₃ powder (“AKP-30” manufactured by Sumitomo Chemical Co., Ltd .: average particle size 0.4 μm, AlN powder (“F grade AlN powder” manufactured by Tokuyama Soda Co., Ltd.): average particle size 0.6 μm), and MgO powder (“Upure Materials Co., Ltd.“ High-purity ultrafine powder ”: average particle size 1.0 μm) were used.

(Mixing conditions) Add 1 kg of alumina cobblestone (purity 99.9%) with a diameter of 5 mm in a 1 liter plastic container, the raw material powder and ethanol (500 cc), mix and disintegrate in a pot mill for 24 hours (70-80 rpm), and mix I got a thing. The mixing ratio of each powder was changed as shown in Table 1.
(Solvent removal / drying)
The preparation was placed in a stainless steel vat and dried at 1050 ° C. for 12 hours in an N ₂ gas dryer.
(Crushing and sieving)
The dried formulation was pulverized using an alumina mortar with a purity of 99.9% and passed through a polyester sieve (# 80).
(Pellet molding)
The preparation was housed in a hand press φ20 mold and molded at a pressure of 200 kg / cm ² to obtain a pellet-shaped molded body. The pellet-like molded body was pressurized with CIP at 2000 kg / cm ² .
(Baking)
A carbon bowl 1 as schematically shown in FIG. 1 was prepared. 3 is a mortar body, and 2 is a lid. The dimensions of the mortar 1 are 300 mm in length, 300 mm in width, and 200 mm in height. A crucible 5 made of boron nitride was accommodated in the mortar 1. As schematically shown in FIG. 2, the boron nitride powder 9 is filled in the space 8 of the main body 7 of the crucible 5, and the pellet-shaped molded body 10 is embedded in the boron nitride powder 9. Then, a lid 6 made of boron nitride is provided. The crucible has a diameter of 80 mm and a height of 70 mm.
(Polishing)
The sintered body of each example was polished until the thickness became 1.2 mm, and then both surfaces of the sintered body were mirror-polished.

In each example shown in Table 1, the following temperature increase-firing-temperature decrease schedule was adopted.
(T-1, T-2)
The temperature was raised from room temperature to 2000 ° C. at a rate of 10 ° C./min, and kept at 2000 ° C. for 10 hours. There is no preheating step.
(T-3, T-4)
The temperature was raised from room temperature to a holding temperature of 1750 ° C. at 10 ° C./min, held at 1750 ° C. for 3 hours, and further raised to a maximum temperature of 2050 ° C. at 10 ° C./min. And it hold | maintained at 2050 degreeC for 6 hours.
(T-5, 6, 7, 8)
The temperature was raised from room temperature to a holding temperature of 1700 ° C. at 10 ° C./min, held at 1700 ° C. for 1 hour, and further raised to a maximum temperature of 2000 ° C. at 2 ° C./min. And it hold | maintained at 2000 degreeC for 10 hours.
(T-9, 10, 11, 11)
The temperature was raised from room temperature to a holding temperature of 1700 ° C. at 10 ° C./min, held at 1700 ° C. for 1 hour, and further raised to a maximum temperature of 2050 ° C. at 2 ° C./min. And it hold | maintained at 2050 degreeC for 3 hours.
(T-13)
The temperature was raised from room temperature to a holding temperature of 1700 ° C. at 10 ° C./min, held at 1700 ° C. for 1 hour, and further raised to a maximum temperature of 2050 ° C. at 1.3 ° C./min. And it hold | maintained at 2050 degreeC for 3 hours.

The following characteristics were measured for the obtained sintered bodies of the respective examples.
(Generation phase)
An X-ray diffraction chart of each sintered body was obtained under the following conditions.
CuKα, 50kV, 300mA, 2θ = 10-70 °
Rotating anti-cathode X-ray diffractometer "RINT" manufactured by Rigaku Corporation
As a result, in each example, each peak of the AlON phase and the Al2O3 phase was detected. Furthermore, the height of each peak was totaled and the total value of the peak height was set to 100%. And each peak height ratio (%) of the AlON phase and the Al ₂ O ₃ phase was measured.
(Particle size)
The particle size of the sintered sample cross section was observed by SEM.
(Density, relative density)
Measured by Archimedes method.
(Linear transmittance)
The fired sample was processed into a size of 13 mm × 13 mm × 1.2 mmt, and the sample whose both surfaces were mirror-polished with diamond paste was measured for transmittance at a wavelength of 600 nm with a linear transmittance meter.

In T-1 of the comparative example, MgO is not added, the temperature is increased to 2000 ° C. at 10 ° C./min, and sintering is performed at 2000 ° C. When the X-ray diffraction analysis of the obtained sintered body was performed, AlON single-phase crystals were not obtained, and it was a composite phase in which Al ₂ O ₃ (Corudum) remained slightly. The peak height ratio of the Al ₂ O ₃ phase was 2%. The linear transmittance of the sample was as low as 1%. In T-2 outside the present invention, MgO is added in an amount of 3.0% by weight, and the same firing conditions as T-1 are employed. When the X-ray diffraction analysis of the obtained sintered body was performed, AlON single-phase crystals were not obtained, and it was a composite phase in which Al ₂ O ₃ (Corudum) remained slightly. The peak height ratio of the Al ₂ O ₃ phase was 1.7%. The relative density was slightly low as 96.0%, and the linear transmittance of the sample reached 21%.

In T-3 of the comparative example, MgO was not added, the temperature was maintained at 1750 ° C. for 3 hours, and the temperature was increased to 2050 ° C. at 10 ° C./min. When the X-ray diffraction analysis of the obtained sintered body was performed, AlON single-phase crystals were not obtained, and it was a composite phase in which Al ₂ O ₃ (Corudum) remained slightly. The peak height ratio of the Al ₂ O ₃ phase was 2%. The linear transmittance of the sample was as low as 1%. In T-4 outside the present invention, 3.0 wt% of MgO is added and sintered under the same conditions as T-3. When the X-ray diffraction analysis of the obtained sintered body was performed, AlON single-phase crystals were not obtained, and it was a composite phase in which Al ₂ O ₃ (Corudum) remained slightly. The peak height ratio of the Al ₂ O ₃ phase was 1.5%. The relative density was slightly low as 96.4%, and the linear transmittance of the sample was 9%.

In T-5 of the example of the present invention, 3.0 wt% of MgO is added, held at 1700 ° C. for 1 hour, and heated up to 2000 ° C. at 2 ° C./min. When the X-ray diffraction analysis of the obtained sintered body was performed, AlON single-phase crystals were not obtained, and it was a composite phase in which Al ₂ O ₃ (Corudum) remained slightly. The peak height ratio of the Al ₂ O ₃ phase was 4.3%. The relative density of the sample was as high as 98.5%, and the linear transmittance of the sample was as high as 41%. In Comparative Examples T-6, 7, and 8, MgO was not added, and sintering was performed under the same conditions as T-5. When the X-ray diffraction analysis of the obtained sintered body was performed, AlON single-phase crystals were not obtained, and it was a composite phase in which Al ₂ O ₃ (Corudum) remained slightly. The peak height ratio of the Al ₂ O ₃ phase was 2.5%. Although the relative density of the sample is high, it is almost the same as the samples T-1 and 3 of the comparative example. On the other hand, in the present invention examples T-2, 4 and 5 in which MgO powder is added, the temperature increase rate to the maximum temperature has a great influence on the relative density of the sample. It is completely different from the example. The linear transmittances of Comparative Examples T-6, 7, and 8 were 5, 2, and 2%, respectively.

In T-9 of the present invention example, 3.0% by weight of MgO was added, held at 1700 ° C. for 1 hour, and increased to 2050 ° C. at 2 ° C./min. When the X-ray diffraction analysis of the obtained sintered body was performed, AlON single-phase crystals were not obtained, and it was a composite phase in which Al ₂ O ₃ (Corudum) remained slightly. The peak height ratio of the Al ₂ O ₃ phase was 4.3%. The relative density of the sample was as high as 99.2%, and the linear transmittance of the sample was as high as 43%. In Comparative Examples T-10, 11, and 12, MgO was not added, and sintering was performed under the same conditions as T-9. When the X-ray diffraction analysis of the obtained sintered body was performed, AlON single-phase crystals were not obtained, and it was a composite phase in which Al ₂ O ₃ (Corudum) remained slightly. Although the relative density of the sample is high, it is almost the same as the samples T-1, 3, 6, 7, and 8 of the comparative example. The linear transmittances of Comparative Examples T-10, 11, and 12 were 5, 3, and 3%, respectively. In Comparative Samples T-10, T-11, and T-12, the Al ₂ O ₃ phase peak height ratios were 4.3%, 2.5%, and 2.5%.
Furthermore, the particle size of the sample was large in T-9 to which 3% by weight of MgO was added, and the particle size of the sample was reduced to about 1/5 in T-10, 11 and 12 to which MgO was not added.

In T-13 of the present invention example, 3.0% by weight of MgO was added, held at 1700 ° C. for 1 hour, and increased to 2050 ° C. at 1.3 ° C./min. When the X-ray diffraction analysis of the obtained sintered body was performed, AlON single-phase crystals were not obtained, and it was a composite phase in which Al ₂ O ₃ (Corudum) remained slightly. The peak height ratio of the Al ₂ O ₃ phase was 4.1%. The linear transmittance of the sample was as high as 31%.

  As described above, according to the present invention, a highly transparent translucent ceramic mainly composed of an aluminum oxynitride phase can be obtained by atmospheric pressure sintering.

It is a fragmentary sectional view showing typically the state where crucible 5 was stored in carbon mortar 1. 2 is a cross-sectional view schematically showing a state in which boron nitride powder 9 and a molded body 10 are embedded in a crucible 5. FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Pot bowl 2 Lid 3 Bowl body 5 Crucible 7 Crucible body 9 Boron nitride powder 10 Molded body

Claims (4)

Al ₂ O ₃ and 80 to 60% of AlN in a molar ratio: in a proportion of 20-40%, and the total amount of MgO powder _Al 2 _{O 3} and AlN having an average particle diameter 0.6~1.2μm When the mixed powder containing 2 to 10 parts by weight is formed into 100 parts by weight, a molded body is obtained, and the molded body is sintered at a maximum temperature of 1950 to 2050 ° C., and 1500 when the temperature is raised to the maximum temperature. A method for producing translucent ceramics, characterized in that the temperature is maintained at a temperature of ˜1750 ° C., and the rate of temperature increase from at least 1700 ° C. to the maximum temperature is 0.5-8 ° C./min . The method according to claim 1, wherein the translucent ceramic has an Al ₂ O ₃ phase. Characterized in that obtained by the method of claim 1, wherein a translucent ceramic. The relative proportion of each peak heights of the AlON phase and the _Al 2 _{O 3} phase is 95.0 to 99.5: characterized in that it is a 5.0 to 0.5, according to claim 3, wherein the translucent ceramics .

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