JP2001270775A - Manufacturing method of YAG transparent sintered body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a transparent sintered body of yttrium-aluminum-garnet used for a laser host material, an arc tube for a discharge lamp, an observation window for a high temperature, an element material for a detector utilizing fluorescence, and the like. An aqueous solution of an acidic salt of yttrium and aluminum is added dropwise to an aqueous solution of a basic salt containing carbonic acid in the range of 0.1 mol / l to 2.5 mol / l, and p is added under conditions where sulfate ions are present.
H was adjusted to 7.4 to 9 to produce a precipitate having a composition corresponding to a mixture of yttrium carbonate and dawsonite at a ratio of 3 to 5, which is an amorphous phase in terms of X-rays. After filtration before the formation of neutral yttrium carbonate, the precipitate is washed and calcined to form a YAG powder, and the YAG powder compact is fired. The filtered amorphous precipitate may be calcined at 800 to 1300 ° C. to obtain a YAG powder having a primary particle size of 40 to 400 nm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to yttrium-aluminum used for a laser host material, an arc tube for a discharge lamp, an observation window for a high temperature, and a detector element material utilizing fluorescence.
The present invention relates to a method for producing a garnet (hereinafter, referred to as YAG) transparent sintered body.

[0002]

2. Description of the Related Art YAG (Y ₃ Al ₅ O
It is known that a high output laser beam can be obtained by adding a lanthanide element such as Nd or Ho to ₁₂ ). Current,
Laser YAG materials are limited to single crystals. The single crystal of YAG is manufactured by a single crystal growing apparatus. BACKGROUND ART In recent years, for the purpose of producing a large amount of laser YAG materials at low cost, technology development for making a YAG powder compact transparent by sintering has been performed.

For example, a method in which an acidic aqueous solution containing yttrium ions and aluminum ions is neutralized with ammonia generated by thermal decomposition of urea to form a precipitate, and the obtained precipitate is calcined to synthesize a YAG powder (Urea uniform precipitation method: see JP-A-2-92817) or a method in which aluminum oxide powder and yttrium oxide powder are mixed so as to have a YAG composition and fired (JP-A-5-2947).
No. 22, JP-A-5-294724, etc.) have been developed. Further, a hot press method of applying pressure during firing (see, for example, Japanese Patent Publication No. 54-8369) has also been developed.

[0004]

However, in the synthesis of a YAG single crystal, the equipment and the iridium crucible used for growing the single crystal are extremely expensive, and it is necessary to grow the crystal at a very high temperature of 2000 degrees Celsius. The growth rate is extremely slow at 0.2 to 0.3 mm / hr, the production cost and the production time are too long, the productivity is low because only one single crystal rod is obtained for one apparatus, and the single crystal is low. There have been various problems such as that a rod having a diameter as small as about 50 mm can be obtained.

[0005] Further, in the above-mentioned homogeneous precipitation method by thermal decomposition of urea, not only is urea consumed in large amounts, but also the reaction temperature and the like must be strictly controlled, and from preparation of solution to formation of precipitate, filtration of precipitate and drying. There was a problem that it took time. Further, there is a disadvantage that a transparent sintered body cannot be obtained unless SiO ₂ is added. On the other hand, the oxide powder mixing method is also an impurity for producing a good transparent sintered body.
0 ₂ must be added, it has a drawback that if Si0 ₂ not added when it is necessary to firing very long time.

[0006]

In order to solve the above-mentioned problems, the production method of the present invention provides an aqueous solution of an acid salt of yttrium and aluminum containing 0.1 to 2.5 mol / l of carbonic acid. The pH is adjusted to 7.4 to 9 under conditions in which sulfate ions are added dropwise to the basic salt aqueous solution, and it is an amorphous phase in terms of X-rays, but a mixture of yttrium carbonate and dawsonite at a ratio of 3: 5. A precipitate having a composition corresponding to the following formula is formed, and the precipitate is filtered before crystalline yttrium carbonate is formed, and then the precipitate is washed and calcined to form a YAG powder, and the molded body of the YAG powder is fired. It is characterized by the following.

In the above-mentioned method for producing a transparent sintered body, the filtered amorphous precipitate is formed in an amount of 800 to 1300.
Primary particles obtained by calcination at 40 ° C.
It is preferable to make the YAG powder of nm.

[0008]

The present inventors have investigated and studied various YAG powders having good sinterability, which can produce a YAG transparent sintered body.
As a result, a YAG powder obtained from a precipitate synthesized under specific conditions, which is amorphous in X-ray but has a chemical composition corresponding to a mixture of yttrium carbonate and dawsonite at a ratio of 3: 5 is preferable. I found that.

That is, an aqueous solution of an acid salt of yttrium and aluminum is dropped into an aqueous solution of ammonium hydrogen carbonate, and the precipitate particles formed under the condition where sulfate ions are present are crystallized, washed, dried and calcined before crystallization. YAG powder. When this YAG powder is used, a YAG transparent sintered body can be manufactured by a normal sintering method without using an additive such as SiO ₂ .

This YAG powder is required for the easily sinterable powder of the composite oxide. (1) There are no strong agglomerated particles in which a large number of primary particles are aggregated. (2) The cause of abnormal grain growth that occurs during firing. Satisfying such a requirement that there is no large compositional fluctuation. Therefore, when a compact of the easily sinterable YAG powder is used, a transparent sintered YAG compact can be manufactured by a normal sintering method without using an additive.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The YAG precursor of the present invention is obtained by mixing a solution obtained by mixing an acidic aqueous solution containing yttrium ions and an acidic aqueous solution containing aluminum ions such that the ratio of yttrium ions to aluminum ions becomes 3 to 5. The solution is added dropwise to a carbonate-containing basic salt aqueous solution having a concentration of 0.1 mol / l to 2.5 mol / l or less and synthesized by a precipitation reaction in a solution in which sulfate ions are present.

As the yttrium acid salt of the raw material of the present invention, one or more of water-soluble inorganic acid salts or organic acid salts such as chlorides, nitrates, sulfates and acetates are used. In addition, one or two or more of water-soluble inorganic acid salts or organic acid salts such as chloride, nitrate, and ammonium alum are used as the acidic salt of aluminum.

The basic carbonate-containing salt used in the present invention includes:
Examples thereof include ammonium carbonate and ammonium hydrogen carbonate, but are not particularly limited as long as they are carbonate-containing basic salts exhibiting the features of the present invention. They are used alone or in combination of two or more.

Examples of the chemical substance that generates sulfate ions used in the present invention include sulfuric acid, ammonium sulfate, aluminum sulfate, yttrium sulfate, and ammonium alum, and the like. Sulfate ions are generated in an aqueous solution exhibiting the characteristics of the present invention. It is not particularly limited as long as it is a chemical substance. They are used alone or in combination of two or more.

It is generally known that when a second phase particle having a diameter corresponding to the wavelength of light is present in a sintered body, the second phase particle becomes a light scattering source. In the present invention as well, it is necessary to use a chemical substance having such a high purity that the second phase particles are not generated even for the raw material for producing the transparent YAG sintered body. Chemical substances having a high solubility in an aqueous solution, such as sodium, potassium, and calcium, can be easily removed by washing, so that their presence in the raw material does not cause much problem.

On the other hand, even if the amount of impurities is such that the solid solution can be dissolved in the sintered body, light-absorbing elements such as Ti and Fe decrease the light transmittance or color. Except for the case where the purpose of use of the material is transparent and colored, such as a transparent coloring material, the amount of such an element needs to be limited to the extent that the purpose of use of the material is not impaired.

In the present invention, the concentration of aluminum ions in the aqueous solution containing yttrium ions and aluminum ions is preferably 0.05 mol / l or more. If the concentration is less than this, the precipitate contains boehmite, which is not preferable because it is very difficult to filter and the YAG powder obtained after calcination contains hard agglomerated particles. The upper limit of the aluminum ion concentration of the solution is not particularly limited, and a preferable result can be obtained even with a saturated solution.

However, since the saturated concentration changes remarkably depending on the temperature, if a solution close to the saturated concentration is used, if the solution temperature is lowered during the precipitation operation, the salt will crystallize and no further work can be performed. There is also. Considering this, the aluminum ion concentration of the solution is particularly preferably 0.01 mol / l to 0.5 mol / l. On the other hand, the yttrium ion concentration is automatically determined from the condition that the concentration ratio of aluminum ion to yttrium ion is 5 to 3.

The concentration of the carbonate-containing basic salt aqueous solution used in the present invention is preferably in the range of 0.1 mol / l to 2.5 mol / l. When the concentration is 0.1 mol / l or less, the amount of carbonate ions during the precipitation reaction is small, and boehmite precipitates instead of the precipitate having the chemical composition of dawsonite required in the present invention. This precipitate is gelatinous and is undesirable because it forms hard agglomerated particles when dried. On the other hand, when the concentration becomes 2.5 mol / l or more, yttrium carbonate grows rapidly, the separation of yttrium and aluminum in the precipitate proceeds, and YA
It is not preferable because the calcination temperature for obtaining the G single-phase powder is increased and the sinterability is reduced.

The YAG precursor according to the method of the present invention needs to be adjusted to a pH of 7.4 to 9 in the presence of sulfate ions. Even when the pH is 7.4 or less, aluminum ions are completely precipitated, but part of the yttrium ions remains in the aqueous solution. Therefore, if the pH is 7.4 or less,
The composition of yttrium and aluminum during precipitation deviates from the composition of YAG, which is not preferable. On the other hand, if the pH is higher than 9, abnormally large yttrium carbonate particles are generated during precipitation, the separation of yttrium and aluminum proceeds, and Y
The calcining temperature for obtaining the AG single phase powder is increased, and the sinterability is deteriorated.

The sulfate ions in the precipitation reaction of the present invention function to aggregate the very fine primary particles of the precipitate to form individually separated rounded aggregated particles having a size of about 0.02 μm to 1 μm. Having. When the precipitate is calcined, the YAG particles formed from the primary particles of the precursor belonging to the same aggregated particles are combined with each other to form one or a small number of YAG primary particles.

However, since the YAG particles produced from the primary particles belonging to another agglomerated particles in this calcination process are not strongly sintered, the YAG powder obtained by calcination has an average particle size. Consists of individually separated particles between 0.02 μm and 0.06 μm.

The amount of sulfate ion used in the present invention is YA
The effect is exhibited if the molar ratio to G is 0.01 or more. The molar ratio is particularly preferably 0.1 or more. However, when the molar ratio is 1 or more, the improvement of the use effect is not recognized for the use amount of the sulfate ion.
It is not preferable in terms of cost.

The precursor produced in the present invention has a chemical composition in which yttrium carbonate and dawsonite are mixed at a ratio of 3: 5. The dried body is an X-ray amorphous phase.
When aging is performed for a long time after the formation of the precipitate, crystalline yttrium carbonate first appears from the amorphous precipitate, and when the ripening is further continued, crystalline dawsonite is recognized. When crystalline yttrium carbonate appears, the separation of yttrium and aluminum in the precipitate proceeds, and it is necessary to calcine at a higher temperature to produce a YAG single phase powder by calcining. As a result, the YAG powder obtained by calcining becomes large and the sinterability deteriorates. For this reason, in the present invention, ripening after precipitation is generated must be limited to 10 hours or less.

If the precipitation reaction temperature in the present invention is 50 ° C. or higher, crystalline yttrium carbonate and dawsonite are formed and grown from the precursor before the washing operation is started, and the separation of yttrium and aluminum proceeds. The calcining temperature at which a single-phase powder can be obtained increases, and the sinterability decreases, which is not preferable. When the temperature is 50 ° C. or lower, it takes a considerable time for the YAG precursor to change from an amorphous state to crystalline yttrium carbonate or dawsonite, which is preferable because the washing can be sufficiently performed.

When the YAG precursor produced by the method of the present invention is calcined, a YAG powder having fine primary particles of 0.01 μm to 0.2 μm and having no aggregated particles is obtained. The calcination temperature is preferably from 900C to 1300C. Calcination temperature is 900 ℃
If the temperature is lower than this, the powder obtained after the calcination is not a single phase of YAG, so that the densification by sintering becomes uneven and the pores cannot be completely removed by sintering. Further, since the particle size is small, the moldability of the particles at the time of producing a molded article is also poor. On the other hand, when calcined at a high temperature of 1300 ° C. or more, primary particles grow violently, the surface free energy, which is the driving force for sintering, becomes small, and sinterability is obtained. Can not.

When the YAG powder produced by the method of the present invention is molded and fired at a temperature of 1500 ° C. or more, a transparent sintered body is obtained. According to the method of the present invention, it is possible to use a conventional sintering method at a considerably lower temperature than the conventional method without adding any additive.
A transparent sintered body is obtained.

[0028]

EXAMPLES Example 1 Ammonium bicarbonate concentration was 1.
200 ml of a 5 mol / l aqueous solution is stirred with a magnetic stirrer. To this solution, 320 ml of an acidic aqueous solution containing 0.15 mol / l ammonium alum and 0.09 mol / l yttrium nitrate is dropped at a rate of 5 ml / min to form a precipitate. The pH at this time was 7.8.
After completion of the precipitation reaction, the liquid in which the precipitate is dispersed is stirred for 30 minutes and then filtered. Disperse the precipitate after filtration in distilled water,
Filter. The dispersion in distilled water and the filtration are repeated four times to wash the precipitate. The finally filtered precipitate is dried in a stream of nitrogen gas at room temperature. The dried precursor was gently loosened in a mortar, and placed in an oxygen stream using a tubular electric furnace.
Calcinate for 2 hours at ℃.

The particle size of the calcined powder was 100 to 200 nm. When this YAG calcined powder is molded at a hydrostatic pressure of 200 MPa and then sintered at 1700 ° C. for 1 hour in a vacuum atmosphere, the sintered density is 99.9% of the theoretical density, and a sintered body excellent in light transmittance is obtained. It was done.

Example 2 Aqueous solution 200 having a concentration of 1.5 mol / l ammonium bicarbonate with a magnetic stirrer
Stir ml. 0.15 aluminum nitrate was added to this solution.
320 ml of an acidic aqueous solution containing mol / l, yttrium nitrate 0.09 mol / l, and ammonium sulfate 0.009 mol / l are dropped at a rate of 5 ml / min to form a precipitate. The pH at this time was 8. The formed precipitate is washed by the method of Example 1, calcined at 1100 ° C. for 2 hours, molded, and sintered by the method of Example 1. A sintered body having substantially the same sintering density and translucency as in Example 1 was obtained.

Comparative Example 1 A YAG precursor and a YAG powder were synthesized under the same conditions as in Example 1 except that aging was performed for 48 hours. When the change in the sintering density due to the calcination temperature was examined, it was found that Y
The powder calcined at 1200 ° C., the lowest temperature at which an AG single phase was obtained, had the best sinterability. Then, when sintering was performed by the method of Example 1 using the YAG powder calcined at this temperature, the sintering density was 98% of the theoretical density, and it was found that the sinterability of the YAG powder was reduced by aging. .

Comparative Example 2: An aqueous solution 10 having a concentration of 0.05 mol / l ammonium bicarbonate using a magnetic stirrer
Stir 00 ml. To this solution, 80 ml of an acidic aqueous solution containing 0.15 mol / l ammonium alum and 0.09 mol / l yttrium nitrate is dropped at a rate of 5 ml / min to form a precipitate. The pH at this time was 7.6. Subsequent processing was performed by the method of Example 1. Example 1
When calcined, molded and sintered under the same conditions as in the above, the bulk density was about 94% of the theoretical density, and the sintered body was white and opaque.

Comparative Example 3: YA was prepared under the same conditions as in Example 1 except that an aqueous solution of ammonium bicarbonate was dropped into the acidic aqueous solution.
G precursor and YAG were synthesized. A precursor in which boehmite and yttrium carbonate were mixed was obtained. In the YAG powder calcined under the conditions of Example 1, fine primary particles were hard and agglomerated. Further, when sintering was performed under the conditions of Example 1, the sintered density was 92% of the theoretical density.

Continuing from the front page (72) Inventor Li Jing Xin 1-1-1 Namiki, Tsukuba-shi, Ibaraki F-Term in the Science and Technology Agency, Inorganic Materials Research Laboratory 4G031 AA08 AA29 BA01 BA14 CA04 GA01 GA02 GA11 4G076 AA02 AA18 BA13 BD02 CA23 DA09 DA11 5F072 AB02 JJ12

Claims (2)

[Claims] 1. An aqueous solution of an acidic salt of yttrium and aluminum is dropped into an aqueous solution of a basic salt containing carbonic acid in the range of 0.1 mol / l to 2.5 mol / l, and the pH is adjusted to 7. The precipitate was adjusted to 4 to 9 to produce a precipitate having an X-ray amorphous phase but a composition corresponding to a mixture of yttrium carbonate and dawsonite at a ratio of 3: 5. The precipitate is washed before it is formed, and the precipitate is washed and calcined to obtain yttrium-aluminum-garnet powder, and the molded product of the yttrium-aluminum-garnet powder is fired, wherein the yttrium-aluminum-garnet powder is fired. Production method of transparent sintered body. 2. The method according to claim 1, wherein the filtered amorphous precipitate is calcined at 800 to 1300 ° C.
A method for producing a yttrium-aluminum-garnet transparent sintered body into yttrium-aluminum-garnet powder having a primary particle size of 40 nm to 400 nm.