JP3563464B2 - Method for producing yttrium-aluminum-garnet powder and yttrium-aluminum-garnet sintered body using the same - Google Patents

Description

【００４３】
実施例２
上記と同様にして、アルカリ中和剤として炭酸ナトリウム溶液の代わりに、水酸化アンモニウム（濃度１０％）を５０００ｇ使用して同様の沈澱物を得た。得られた沈澱物は１３５６ｇであった。この沈澱物をアルミナ製匣鉢を用いて１０００℃の温度で２時間仮焼した。仮焼によって得られた酸化物は２８９ｇであった。
【００４４】
これを高純度アルミナボール６００ｇとＩＰＡ３００ｇとともにポリポットに投入し、回転ミルで２４時間粉砕した。粉砕した粉末を３２５メッシュに通して乾燥させた後、８０メッシュを通して均一な粉末を得た。
【００４５】
この粉末を一軸プレス及びＣＩＰを用いて２．５ｇ／ｃｍ^３ 以上の生密度の成形体を作製した。この成形体を焼成温度１８００℃、焼成時間１０時間、昇温速度５０℃／時、真空雰囲気中で焼成した。
【００４６】
得られた焼結体を厚み１ｍｍに研磨した後、１μｍのダイヤモンドペーストで鏡面仕上げを行った。この焼結体の波長６００ｎｍの可視光の直線透過率を測定したところ、８１％と極めて高い透光性を示した。
【００４７】
【発明の効果】
以上のように本発明によれば、水酸化アルミニウム粉末とイットリウム化合物溶液を混合し、中和して沈澱物を生成した後、得られた沈澱物を仮焼する工程からＹＡＧ粉末を製造することによって、水酸化アルミニウム粉末が核となって沈澱物が生成するため、均一な粒状沈澱物を容易に製造することができ、均一なＹＡＧ粉末を得ることができる。
【００４８】
そのため、このＹＡＧ粉末を用いて焼成すれば、低温、短時間の焼成で優れた透光性の焼結体を得られるため、結晶粒子が小さく、強度、硬度の高いＹＡＧ焼結体を得ることができる。[0001]
[Industrial applications]
The present invention relates to a method for producing yttrium-aluminum-garnet (hereinafter, referred to as YAG) powder, and a YAG sintered body having excellent translucency using the YAG powder.
[0002]
[Prior art]
Conventionally, since YAG (Y ₃ Al ₅ O ₁₂ ) has a cubic crystal form, it hardly causes grain boundary scattering and is a good transparent body. Therefore, attempts have been made to obtain a translucent sintered body by various manufacturing methods. ing.
[0003]
Such a YAG is prepared by a single crystal method, a method of mixing an Al ₂ O ₃ powder and a Y ₂ O ₃ powder, and performing a HIP treatment or a hot press baking (Japanese Patent Application Laid-Open Nos. 3-275560 and 3-275561). Publications, etc.).
[0004]
However, there is a problem in that the single crystal synthesis is expensive and it is difficult to manufacture the crystal in an arbitrary shape. Further, in the case of the HIP process, there is a problem that the apparatus becomes large and productivity is not good. Further, in the case of hot press firing, there is a disadvantage that carbon enters the sintered body from carbon used for the molding die, and the transparency is reduced.
[0005]
Therefore, YAG powder is manufactured in advance, and a sintered body is obtained using the YAG powder.
[0006]
For example, in order to produce YAG powder by coprecipitation, an acidic aqueous solution containing yttrium ions and aluminum ions is neutralized with urea to form a precipitate, and the obtained precipitate is calcined to synthesize YAG. Method (urea precipitation method: see Japanese Patent Application Laid-Open No. 2-92817) or a method in which an acidic aqueous solution containing yttrium ions and aluminum ions is neutralized with sodium hydroxide or aqueous ammonia to form a precipitate. There is a method of synthesizing YAG by calcining (alkali coprecipitation method).
[0007]
Furthermore, there is a method in which alumina powder and yttria powder are mixed, then calcined at 1000 to 1600 ° C., and pulverized to produce a YAG powder (powder mixing method: see JP-A-6-107456).
[0008]
[Problems to be solved by the invention]
However, the above-mentioned urea precipitation method has problems that control of the sulfate ion, the amount of urea, the reaction temperature, and the like are required, and that it takes time from the start of heating the adjusted solution to the formation of the precipitate and the removal of the precipitate. Was. Further, in the above urea precipitation method, since in order to obtain a precipitate of granular is required sulfate ion, SO _X gas is a drawback that occurs during the calcining precipitate. Further, there is also a disadvantage that a sintered body cannot be obtained unless SiO ₂ is added when firing the obtained YAG powder.
[0009]
Further, in the alkaline coprecipitation method, since only a gel-like precipitate is obtained, there is a disadvantage that the filterability is poor and impurities cannot be sufficiently removed during the precipitation.
[0010]
Further, the powder mixing method has problems that a long time is required for uniform mixing, that uniformization cannot be sufficiently achieved, and that impurities are easily mixed.
[0011]
In addition, since it is difficult to obtain a uniform YAG powder by the above method, when sintering using this YAG powder, sintering at a high temperature for a long time is necessary, and the resulting sintered body has an average crystal grain size. The diameter was as large as 50 to 60 μm, and the mechanical properties such as strength and hardness were low.
[0012]
[Means for Solving the Problems]
The present inventors have sufficiently studied such a problem, and as a result, alkali-neutralize a mixed solution of the aluminum hydroxide powder and the yttrium compound solution, and calcine the obtained precipitate. It has been found that by obtaining a YAG powder, a commercially available YAG powder can be obtained at low cost without using the powder mixing method or the urea precipitation method as described above.
[0013]
In other words, while the conventional coprecipitation method mixes the solutions, in the present invention, the aluminum hydroxide powder and the yttrium compound solution are mixed, and the powder and the solution are mixed and neutralized with alkali, It is characterized in that a precipitate is obtained (hereinafter, referred to as a semi-coprecipitation method). Therefore, the aluminum hydroxide powder present in the mixed solution becomes a nucleus, and the yttrium compound solution adheres to the surface of the nucleus or enters a state in which the yttrium compound solution penetrates into the nucleus. A precipitate will form on the surface. Therefore, a precipitate having a uniform composition is obtained in the liquid phase, and the core of aluminum hydroxide also plays a role in improving the filterability.
[0014]
Further, according to the semi-coprecipitation method of the present invention, sulfate ions are not required to obtain a granular precipitate, and generation of SO _X gas during calcining the precipitate can be prevented. This is because the size and shape of the precipitate are determined by the size and shape of the aluminum hydroxide powder, so that it is not necessary to control with sulfate ions during the process. According to the semi-coprecipitation method of the present invention, a granular precipitate can be obtained, so that secondary aggregation during calcination can be prevented.
[0015]
Furthermore, since the YAG powder obtained by the semi-coprecipitation method of the present invention can have a uniform composition, it can be fired at a relatively low temperature and in a short time, and the average crystal grain size of the sintered body is set to 30 μm or less, and the strength and hardness are reduced Can be higher. In addition, since the YAG powder obtained by the semi-coprecipitation method of the present invention can be fired without adding an additive such as SiO ₂ , the final YAG sintered body should be composed of 100% YAG excluding impurities. Can be.
[0016]
As the aluminum hydroxide powder used in the production method of the present invention, a powder having an Al purity of 95.0% or more, preferably 99.0% or more is used. This is because if the Al purity is less than 95.0%, control during firing cannot be performed due to the influence of impurities. Further, as the aluminum hydroxide powder, those having an amount of impurities of Na ₂ O and SiO ₂ of 5.0% or less, preferably 1.0% or less, respectively, are used. This is because when Na ₂ O or SiO ₂ is present in an amount of more than 5.0%, the powder reacts with a crucible or a sagger during calcining of the powder, adheres to the powder, or has a glass phase at a grain boundary when the compact is fired. Is generated, alumina silicate is present to cause devitrification, and grain growth occurs, making it impossible to form a uniform structure.
[0017]
Further, the aluminum hydroxide powder has an average particle diameter of 0.1 to 100 μm, preferably 0.4 to 30 μm. This is because if the average particle size is less than 0.1 μm, coagulation occurs and uniformization cannot be achieved, while if it exceeds 100 μm, uniformity during stirring and mixing becomes difficult.
[0018]
As the yttrium compound solution, an acidic solution containing one or more of acidic yttrium solutions such as an yttrium halide solution, an yttrium sulfate solution, an yttrium nitrate solution, and an yttrium acetate solution is used. In addition, as the yttrium halide solution, there are yttrium fluoride, yttrium chloride, yttrium bromide, yttrium iodide and the like. . This is because yttrium fluoride has low solubility and dissolved fluorine ions react with aluminum hydroxide to form aluminum fluoride, which is difficult to control.
[0019]
In addition, the purity of yttrium in the yttrium compound solution is 95.0% or more, preferably 99.0% or more. This is because if the purity of yttrium is less than 95.0%, it becomes difficult to control the sintering due to the influence of impurities, and uniform YAG cannot be generated.
[0020]
Next, the above-mentioned aluminum hydroxide powder and the yttrium compound _solution, the weight ratio of Y 2 _{O 3} and in terms _{of Al} 2 _{O 3} with _Y 2 _O 3 / _Al 2 _{O 3} and a range of 1.27 to 1.50 Mix so that This is because if the weight ratio is out of the above range, YAM (yttrium-aluminum-monoclinic) crystals are formed in the sintered body, or the presence of excess Y ₂ O ₃ or Al ₂ O ₃ is caused by sintering. This is because it affects the body and inhibits the formation of devitrified and homogeneous YAG. Note that the aluminum hydroxide powder in the above mixed solution is hardly dissolved, and becomes a white slurry solution.
[0021]
Next, the mixed solution is stirred for 30 minutes or more, and alkali neutralization is performed in a state where the aluminum hydroxide powder does not settle and is maintained to have a uniform composition.
[0022]
Examples of the alkali neutralizer include alkali metal hydroxides represented by sodium hydroxide, alkali metal carbonates represented by sodium carbonate, alkali metal bicarbonates represented by sodium hydrogen carbonate, and hydrogen carbonate One or more solutions of an organic compound exhibiting alkalinity, such as ammonium, ammonium hydroxide, hydroxides or carbonates of alkaline earth metals, are used. Preferably, use of sodium hydroxide, sodium carbonate, sodium hydrogen carbonate, ammonium hydroxide, and ammonium hydrogen carbonate facilitates removal of impurities and is economical.
[0023]
The neutralization reaction using an alkali neutralizing agent for the mixed solution is performed by a method of adding one of the solutions to the other, a continuous neutralization in a liquid feed pipe such as a static mixer, or the like. However, at the time of neutralization, it is desirable to continue stirring and mixing the solution in order to maintain uniformity.
[0024]
The reaction temperature is from 0 to 100 ° C., preferably from 10 to 50 ° C. When the temperature exceeds 100 ° C., the above-mentioned acidic gas is generated from the mixed solution, or when an ammonium compound is used as an alkali agent, ammonium gas is used. This is because, when the temperature is lower than 0 ° C., the neutralization reaction does not sufficiently occur.
[0025]
Further, the pH at the time of the neutralization reaction is set to 5 to 10, preferably 6 to 9.5. This is because if the pH is less than 5, the neutralized yttrium precipitate will be redissolved, whereas if the pH exceeds 10, redissolution of aluminum will begin, in any case causing the composition to fall outside the required range. It is.
[0026]
Note that the required amount of the alkali neutralizer is affected by the acidity of the yttrium compound solution. Therefore, the required amount of the alkali neutralizer is determined by defining the pH at the time of neutralization as described above.
[0027]
Next, after the alkali neutralization, the mixture is stirred for at least 30 minutes or more, and the precipitate is filtered and washed with water. In this filtration method, a device such as a Buchner funnel is used, or a vacuum filter such as a belt filter, a filter press, a centrifugal dehydrator, or the like is used, and the device is simultaneously washed with water. At the time of washing with water, ion-exchanged water is usually used, but an ammonia compound solution having a pH of 5 to 10 may be used. In any case, washing with water is sufficiently performed.
[0028]
The precipitate cake obtained after filtration and water washing is white and has a different water content depending on the average particle size of aluminum hydroxide and the dewatering capacity of the filter, but does not affect the physical properties after calcination.
[0029]
Next, the cake of the precipitate is calcined at 700 to 1500 ° C. in order to convert the precipitate, which is a hydroxide or a carbonate, into an oxide. , YAG to suppress abnormal grain growth and maintain activation. At this time, the calcination temperature was set to 700 to 1500 ° C. If the temperature was lower than 700 ° C., the oxidation was insufficient, and the synthesis of YAG became difficult. This is because the sinterability deteriorates and the pulverizability deteriorates.
[0030]
By this calcination, hydroxides and carbonates of Y and Al become Y ₂ O ₃ and Al ₂ O ₃ , respectively, which further changes from YAM to YAG. At this time, by expanding the volume at the time of change from YAM to YAG, firing can be performed without causing volume expansion in the firing after forming, thereby suppressing the generation of voids and defects in the sintered body and uniformity. Thus, a fired body having a simple structure can be produced.
[0031]
Through the above steps, the obtained YAG is pulverized into a raw material powder, formed into a predetermined shape, and fired at 1600 to 1900 ° C. in a reducing atmosphere such as hydrogen, nitrogen, or a vacuum to obtain a YAG sintered material. You can get the body.
[0032]
Here, the sintering temperature is set to 1600 to 1900 ° C., because if it is less than 1600 ° C., sintering is insufficient and sufficient densification cannot be performed. If it exceeds 1900 ° C., abnormal grain growth occurs, and pores are formed. This is because the fine particles are taken in and the denseness is reduced. In addition, firing in a reducing atmosphere is because hydrogen and nitrogen diffuse more quickly than in the air, so that densification easily occurs, and the same applies in vacuum.
[0033]
The YAG sintered body thus obtained has a high translucency of 70% or more in linear transmittance of visible light per 1 mm in thickness, has an average crystal particle diameter of 30 μm or less, and has high strength and hardness. have. Therefore, it can be suitably used as a member for various industrial machines, such as a window material for a timepiece, a discharge tube of a high pressure discharge lamp, and an optical fiber connector member, or a member for various decorations.
[0034]
【Example】
Hereinafter, embodiments of the present invention will be described.
[0035]
Example 1
Yttrium hydrochloride solution (Y ₂ O ₃ content containing 199.5 g of aluminum hydroxide powder having a purity of 99.5%, an average particle diameter of 0.6 μm, and a BET specific surface area of 8.0 m / g, and a purity of 99.5% yttrium) (10%) was mixed with 1712 g with stirring. To this mixture, 5000 g of a sodium carbonate solution (concentration: 10%) was added as an alkali neutralizer, and the mixture was stirred and mixed for 30 minutes. The pH at this time was 7.5.
[0036]
Next, the obtained precipitate was separated by filtration using a Buchner funnel, and further washed with 2000 g of pure water. The obtained precipitate weighed 1540 g.
[0037]
This precipitate was calcined at various temperatures of 500 to 1700 ° C. for 2 hours using an alumina sagger. 600 g of high-purity alumina balls and 300 g of isopropyl alcohol (IPA) as a solvent were put into a polypot and pulverized by a rotary mill for 24 hours. After the powder after pulverization was passed through 325 mesh and dried, a uniform YAG powder was obtained through 80 mesh.
[0038]
Using the YAG powder thus obtained, a green compact of 2.5 g / cm ³ or more was produced by using a uniaxial press and a cold hydraulic press (CIP). This molded body was fired at a temperature of 1600 to 1900 ° C. for 2 to 20 hours in a firing temperature, a firing time, a heating rate and a firing atmosphere shown in Table 1.
[0039]
When the obtained sintered body was measured with an X-ray diffractometer, formation of YAG was confirmed. Further, the obtained sintered body was polished to a thickness of 1 mm, mirror-polished with a diamond paste having a particle size of 1 μm, and then the linear transmittance of visible light having a wavelength of 600 nm was measured.
[0040]
The results are as shown in Table 1. In Table 1, those that were not calcined (No. 1), which were out of the range of the present invention, those whose calcining temperature was out of the range of 700 to 1500 ° C. (Nos. 13 and 14), In all cases where the atmosphere was not reducing (No. 15), the light transmittance of the sintered body was poor.
[0041]
On the other hand, all of the samples obtained by the production method of the present invention exhibited excellent translucency in which the linear transmittance of the sintered body was 70% or more.
[0042]
[Table 1]

[0043]
Example 2
In the same manner as described above, a similar precipitate was obtained by using 5000 g of ammonium hydroxide (concentration: 10%) instead of a sodium carbonate solution as an alkali neutralizing agent. The obtained precipitate weighed 1356 g. The precipitate was calcined in an alumina sagger at a temperature of 1000 ° C. for 2 hours. The oxide obtained by calcination was 289 g.
[0044]
This was put into a polypot together with 600 g of high-purity alumina balls and 300 g of IPA, and pulverized by a rotary mill for 24 hours. After the pulverized powder was dried by passing through 325 mesh, a uniform powder was obtained through 80 mesh.
[0045]
This powder was formed into a green body having a green density of 2.5 g / cm ³ or more by using a uniaxial press and CIP. This molded body was fired in a vacuum atmosphere at a firing temperature of 1800 ° C., a firing time of 10 hours, a heating rate of 50 ° C./hour.
[0046]
The obtained sintered body was polished to a thickness of 1 mm, and then mirror-finished with a 1 μm diamond paste. The linear transmittance of this sintered body for visible light having a wavelength of 600 nm was measured and found to be extremely high at 81%.
[0047]
【The invention's effect】
As described above, according to the present invention, the aluminum hydroxide powder and the yttrium compound solution are mixed and neutralized to form a precipitate, and then the obtained precipitate is calcined to produce a YAG powder. As a result, a precipitate is formed with the aluminum hydroxide powder as a nucleus, so that a uniform granular precipitate can be easily produced, and a uniform YAG powder can be obtained.
[0048]
Therefore, if this YAG powder is fired, an excellent translucent sintered body can be obtained at a low temperature and in a short time, so that a YAG sintered body having small crystal grains, high strength and high hardness can be obtained. Can be.

Claims (3)

A method for producing yttrium-aluminum-garnet powder, comprising the steps of mixing an aluminum hydroxide powder and a yttrium compound solution, neutralizing to form a precipitate, calcining the obtained precipitate and pulverizing the precipitate. Aluminum hydroxide powder having an average particle diameter 0.1~100μm a purity 95.0% or more, and a purity of 95.0% or more yttrium compound _solution, Y 2 _{O 3} and in terms _{of Al} 2 _{O 3} with _Y 2 _{O 3} / Al ₂ O ₃ was mixed so that the weight ratio was in the range of 1.27 to 1.50, and the mixture was neutralized with alkali to a pH in the range of 5 to 10, and then the obtained precipitate was filtered. The method for producing yttrium-aluminum-garnet powder according to claim 1, wherein the powder is calcined at 700 to 1500 ° C and pulverized. A yttrium-aluminum-garnet sinter obtained by molding the yttrium-aluminum-garnet powder obtained by the production method according to claim 1 or 2 into a predetermined shape, and firing in a reducing atmosphere at a temperature of 1600 to 1900 ° C. Union.