JPH11322308A - Production of compound metal oxide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a process for producing ultrafine compound metal oxide particle having a single-phase structure at a low cost. SOLUTION: Plural kinds of metallic compounds are dissolved in an aqueous solution of a polyol to effect the reaction of the polyol with the metallic compounds. The metal complex produced by the reaction is gelled by removing water and the obtained compound metal oxide precursor is baked to produce the objective compound metal oxide. Preferably, the polyol is ethylene glycol and/or propylene glycol and the precursor is baked at temperatures of 400-1400 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a composite metal oxide, and more particularly to a method for producing an ultrafine composite metal oxide having a single phase and a uniform chemical composition.

[0002]

2. Description of the Related Art Composite metal oxides, particularly composite metal oxides containing a metal whose valence is liable to change, such as transition metals, include fluorescent materials, magnetic materials, dielectric materials, photocatalysts, conductors, and filter pigments. It is used for

[0003] In the case of phosphors, for example, in the case of phosphors, those having a high degree of single phase and a uniform chemical composition with the ultra-high definition of the display and being finely divided into ultra-fine particles may be used. Required.

Conventionally, a phosphor has generally been produced by a solid-to-solid reaction by mixing raw materials such as an oxide containing a constituent metal element and then firing the mixture at a high temperature of 1400 ° C. or higher. (Solid phase method). However, in this method, it is necessary to perform calcination at a high temperature for a long time in order to perform a solid-solid reaction, and as a result, the particle diameter of the phosphor increases. In order to obtain particles having a small particle size, pulverization, classification, and the like are further performed. However, in these methods for reducing the particle size, it is difficult to adjust the particle size, and the yield is low.

On the other hand, the following liquid phase method is also known as a method for producing a composite metal oxide. (A) dissolving a plurality of organic acid metal salts in an organic solvent, and then heating to evaporate a part of the organic solvent to form a gel-like composite metal oxide precursor, which is thermally decomposed to form a composite; Citric acid method for producing metal oxides (Journal of the Japan Institute of Metals, 26th edition)
Vol. 10, No. pp. 943-949), (b) A hydroxide or oxalate of a metal is coprecipitated by adding a precipitating agent such as alkali or oxalic acid to an aqueous solution of a plurality of metal salts, and the resulting precipitate is calcined and oxidized. (C) an alkoxide method of reacting a plurality of metal compounds with an alcohol to produce a metal alkoxide and thermally decomposing the metal alkoxide, (d) a plurality of metal salts and / or alkoxides, and oxycarboxylic acid or A complex polymerization method in which a polyol is added to a solvent containing a polyamino chelating agent to carry out polymerization (Japanese Patent Laid-Open No.
No. 5934).

[0006] Among these liquid phase methods, the (a) citric acid method and (c) alkoxide method have a difference in the solubility of each raw material compound when the organic solvent in the raw material is removed. It is difficult to obtain a metal oxide, and the production of a composite metal oxide is complicated. Further, (b) the coprecipitation method has a narrow operation range of coprecipitation, so that applicable metal elements are limited, and it is difficult to freely select a combination of metal elements and a ratio of metal elements. Oxide cannot be obtained. Further, in the complex polymerization method (d), in order to obtain a composite metal oxide having a uniform composition, a large amount of an organic substance must be used to polymerize the obtained complex. Are required to improve.

[0007]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-mentioned drawbacks of the liquid phase method and to provide a method for producing a single-phase and ultrafine composite metal oxide at low cost. Things.

[0008]

The present invention has succeeded in solving the above-mentioned problems by employing the following constitutions. (1) dissolving a plurality of metal compounds in a polyol aqueous solution,
Reacting a polyol with the metal compound to form a metal complex, removing water to form a gel, producing a precursor of the composite metal oxide, and then calcining the precursor. Manufacturing method.

(2) The method for producing a composite metal oxide according to (1), wherein the polyol is ethylene glycol and / or propylene glycol. (3) wherein the metal compound is a water-soluble carbonate, nitrate, sulfate, or carboxylate (1)
Or the method for producing a composite metal oxide according to (2).

(4) The method for producing a composite metal oxide according to any one of (1) to (3), wherein the metal complex is subjected to a gelling treatment at a temperature of 150 to 300 ° C. (5) The method for producing a composite metal oxide according to any one of (1) to (4), wherein the precursor is calcined at a temperature of 400 to 1400 ° C.

(5) The composite metal oxide has a particle diameter of 50 to 50
The method for producing a composite metal oxide according to any one of the above (1) to (4), wherein the composite metal oxide is fired so as to have a range of 800 nm. (6) The method for producing a composite metal oxide according to any one of (1) to (5), wherein the composite metal oxide is a phosphor.

[0012]

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a precursor of a composite metal oxide by dissolving and reacting a plurality of metal compounds in an aqueous polyol solution to form a metal complex, removing water and gelling the complex. By firing the precursor, a single-phase and ultrafine composite metal oxide can be produced at low cost.

The composite metal oxide used in the present invention, for example,
In the case of the phosphor, the compound of the metal element constituting the host and the activator may be a water-soluble carbonate, nitrate, sulfate or carboxylate of the metal element (preferably a carboxylate having 1 to 6 carbon atoms, In particular, acetate) can be used. Among them, nitrates, acetates, and other carboxylate salts are preferable from the viewpoint of decomposability during firing.

The metal elements constituting the composite metal oxide of the present invention include Ti, V, Cr, Mn, Fe, Co, N
i, transition metal such as Cu, Zr, Nb, Mo, Hf, Ta, W, Ga, Ge, In, Sn, Sb, Tl, Pb, B
Typical metals such as i and Po, and Gd, Eu, Tb, Sm, Pr, Ce, and Yb used for the base material and activator of the phosphor
Rare earth (lanthanoid) metals such as

The polyols used in the present invention include ethylene glycol (boiling point: 197 ° C.), propylene glycol (boiling point: 188 ° C.), trimethylene glycol (boiling point: 210 ° C.), 1,4-butadiol (boiling point; 235 ° C.), 1,5-pentadiol (boiling point: 24
1 ° C), 1,6-hexanediol (boiling point: 132 ° C)
And the like. Among them, ethylene glycol is particularly preferred in terms of uniformity and cost. In addition, propylene glycol is preferable in terms of environmental safety.

The total amount of the polyol added is 0.5 to the total number of moles of the metal element constituting the composite metal oxide.
A range of 30 to 30 times, preferably 5 to 10 times is appropriate.
If the amount of the polyol is less than 0.5 times, the gelling reaction is unlikely to occur, and there is a possibility that a uniform compound is not formed. However, the production cost of the composite metal oxide increases, which is not preferable.

The gelation treatment is carried out by heating water containing metal element ions and polyol. The temperature at this time is 150 to 300 ° C. in consideration of the boiling point of the polyol, preferably 2 to 300 ° C.
The range of 00 to 250 ° C is appropriate. In addition, after evaporating water to an appropriate degree, a precursor of the composite metal oxide can be obtained by means of spray drying, vacuum drying, freeze drying or the like.

Next, the precursor is fired to obtain a composite metal oxide powder. The firing temperature at this time depends on the type of the composite metal oxide, but is 400 to 1400 ° C., preferably 700 to 1400 ° C.
A range of 1100 ° C. is appropriate. This firing temperature is 400
If the temperature is lower than ℃, the precursor cannot be thermally decomposed and oxidized,
If it exceeds 1400 ° C., there is a possibility that the grain growth may progress abnormally, or the constituent components may evaporate and not form a single phase. The firing atmosphere does not necessarily need to be in the air, and may be performed in a neutral atmosphere or a reducing atmosphere as needed.

Further, in the present invention, a single-phase composite metal oxide particle having a uniform composition is obtained by controlling the firing temperature, the atmosphere and the like to adjust the particle diameter of the composite metal oxide to 50 to 800 nm. In particular, in the phosphor particles, the respective metal elements constituting the matrix and the activator are uniformly mixed, and the emission luminance and color tone with high purity are inferior to those obtained by the conventional solid phase method. It has become possible to produce low-priced phosphors at low cost.

The composite metal oxide produced by the method of the present invention can be applied to, for example, the following applications. (1) Phosphor: Blue light-emitting phosphor BaMgAl ₁₄ O ₂₃ : Eu, green light-emitting phosphor Y ₃ Al ₅ O ₁₂ : Ce, Y ₃ Al ₅ O
₁₂ : Tb red-emitting phosphor Y ₂ O ₃ : Eu and the like. (2) Display filter pigment: Al ₂ O ₃ .Co
O-based pigments, Fe ₂ O ₃ .Al ₂ O ₃ -based pigments and the like.

[0021]

EXAMPLES (Example 1) A suitable amount of water was placed in a beaker.
Ethylene glycol was added to a concentration of 0 mol / kg, and the mixture was stirred until it was completely dissolved. Next, yttrium nitrate hexahydrate and europium nitrate hexahydrate were sequentially added to this solution, and the mixture was stirred until completely dissolved to obtain a colorless and transparent solution. The solution was added so that the Y concentration was 1.0 mol / kg and the Eu concentration was 0.04 mol / kg.

This solution was placed on a hot plate maintained at 200 ° C. together with the beaker, and evaporated to dryness to obtain a precursor of a composite metal oxide. Put this precursor in an alumina boat,
Heat treatment at 350 ° C. for 2 hours using an electric furnace to obtain amorphous Y
₂ O ₃ : Eu was obtained. Then, it was fired in the air at 600 ° C. for 2 hours to obtain a Y ₂ O ₃ : Eu red light emitting phosphor. Emission color (emission chromaticity point expressed in CIE color system) and emission luminance when this phosphor is irradiated with ultraviolet light of 254 nm,
In addition, the particle size of the phosphor converted from the measured value of the specific surface area by the BET method (BET method converted value) was determined, and the results are shown in Table 1. The emission luminance was shown as a relative value with respect to the phosphor obtained in Comparative Example 1 below. If the light emission luminance is about 60% or more, the function as a phosphor is exhibited.

Example 2 A Y ₂ O ₃ : Eu phosphor was obtained in the same manner as in Example 1 except that the firing temperature of the precursor was changed from 600 ° C. to 900 ° C. The emission luminance, emission color and BET-converted particle size of the obtained phosphor were measured in the same manner as in Example 1, and the results are shown in Table 1.

Example 3 A Y ₂ O ₃ : Eu phosphor was obtained in the same manner as in Example 1 except that the firing temperature of the precursor was changed from 600 ° C. to 1100 ° C. The obtained phosphor was subjected to light emission luminance, light emission color and B light emission in the same manner as in Example 1.
The ET-equivalent particle size was measured, and the results are shown in Table 1.

Example 4 A Y ₂ O ₃ : Eu phosphor was obtained in the same manner as in Example 1 except that the firing temperature of the precursor was changed from 600 ° C. to 1400 ° C. The obtained phosphor was subjected to light emission luminance, light emission color and B light emission in the same manner as in Example 1.
The ET-equivalent particle size was measured, and the results are shown in Table 1.

(Comparative Example 1) An oxide powder of Y ₂ O ₃ and Eu ₂ O ₃ was weighed out so that the metal element in the raw material mixture had the same stoichiometric composition as in Example 1, and was fluorinated. Barium fluoride was added and mixed as a flux, packed in an alumina crucible, and fired at 1500 ° C. for 2 hours in the air.
_{A 2} O ₃ : Eu phosphor was obtained. The emission luminance, emission color and BET-converted particle size of the obtained phosphor were measured in the same manner as in Example 1, and the results are shown in Table 1.

(Comparative Example 2) Ethylene glycol (EG) and citric acid (CA) were used as solvents in a beaker by EG: C
A: weigh out to a molar ratio of 40:10, keep it on a hot stirrer at about 40 ° C., and add citric acid (C
Stir until A) is completely dissolved. Next, yttrium nitrate hexahydrate and europium nitrate hexahydrate, which are raw metal compounds, were added to this solution with EG: CA: Y: Eu =
40: 10: 1: 0.04 were added sequentially in such a ratio as to give a molar ratio, and the mixture was stirred at 40 ° C. until these were completely dissolved to obtain a colorless and transparent solution.

The solution was placed on a hot stirrer for about 130
The polymerization reaction was allowed to proceed by heating and stirring at ℃. With the progress of the polymerization reaction, the viscosity of the solution increased, and after several hours, a complex polymer of a resinous solid containing brown europium (Eu) and yttrium (Y) was formed. Next, this brown resinous solid was heated at 350 ° C. for several hours using a mantle heater,
The mixture was loosened while removing the solvent and excess organic substances to obtain a black powdery solid. This black powdery solid was placed in an alumina boat and calcined at 900 ° C. for 2 hours using an electric furnace, whereby Y ₂ O ₃ : Eu having a BET equivalent particle diameter of 350 nm was obtained.
A phosphor was obtained. With respect to the obtained Y ₂ O ₃ : Eu phosphor,
Light emission luminance, light emission color and BET as in the case of the first embodiment.
The converted particle size was measured, and the results are shown in Table 1.

[0029]

[Table 1]

As is clear from Table 1, each of the phosphors of the examples has a particle size of 1000 nm (1 μm) or less, and when the phosphor is produced by the production method of the present invention, the ultrafine particles of the phosphor are produced. I got the body. In addition, the emission color of each phosphor of the example is the same as that of the phosphor of the comparative example 1 according to the conventional method, and the emission luminance is 60% or more, which is a practical emission luminance. Is presumed to be sufficiently single-phased and have a uniform chemical composition. In addition, the phosphor of Comparative Example 2 was substantially the same in terms of emission luminance level, emission color, and particle size as the phosphors of each of the Examples, but the amount of organic substances used was large. It was not favorable in terms of cost and other points.

[0031]

According to the present invention, by adopting the above-mentioned constitution, it has become possible to produce a single-phase and ultrafine composite metal oxide at low cost.

Continued on the front page (72) Inventor Takeka Matsumoto 1060 Narita, Odawara-shi, Kanagawa Inside Kasei Optonics Co., Ltd.

Claims (5)

[Claims] 1. A precursor of a composite metal oxide was produced by dissolving a plurality of metal compounds in an aqueous solution of a polyol, reacting the polyol with the metal compound to form a metal complex, removing water and gelling. And baking the precursor thereafter. 2. The method for producing a composite metal oxide according to claim 1, wherein the polyol is ethylene glycol and / or propylene glycol. 3. The method according to claim 1, wherein the precursor is calcined at a temperature of 400 to 1400 ° C. 4. The composite metal oxide has a particle diameter of 50-8.
The method for producing a composite metal oxide according to any one of claims 1 to 3, wherein the firing is performed so as to be in a range of 00 nm. 5. The method for producing a composite metal oxide according to claim 1, wherein the composite metal oxide is a phosphor.