JPH0797211A - Production of rare earth element oxide - Google Patents

Abstract

PURPOSE:To produce a rare earth element oxide consisting of globular particles having relatively large diameter and useful as a raw material for fluorescent substances. CONSTITUTION:Urea is added to an aqueous solution of a salt of rare earth element containing sulfuric acid ion and the solution is heated and then, the produced precipitation is burned to provide the rare earth element oxide.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a spherical rare earth element oxide having a relatively large particle size, which is useful as a phosphor material.

[0002]

2. Description of the Related Art It is known as the urea method that when urea is added to an aqueous solution of a salt of a rare earth element and heated, the carbonate and hydroxide ions generated by hydrolysis of urea cause the rare earth element to form a double salt and precipitate. Has been.

[0003]

However, although the precipitate obtained by the urea method and the oxide obtained by firing the same have a spherical particle shape, the average particle diameter is at most 1 μm or less. This is too small in the case of yttrium oxide as a phosphor raw material. The present invention is intended to provide a spherical rare earth element oxide having an average particle diameter of 2 to 10 μm, which is suitable for yttrium oxide as a phosphor raw material.

[0004]

In order to solve such a problem, the present inventor has made various kinds of anions coexist and react during precipitation of a rare earth element by the urea method, and the shape and particle size of the particles produced. As a result of studying the effect on the above, it was found that a relatively large spherical particle is produced when a sulfate ion coexists, and the present invention was completed by carefully examining various conditions. The gist of the present invention is a method for producing a rare earth element oxide, which comprises adding urea to an aqueous solution of a salt of a rare earth element containing a sulfate ion, heating the mixture, and calcining a precipitate formed therein.

The present invention will be described in detail below. 0.01 to 0.
To a solution of a salt of a rare earth element of 5 mol / L, 5 to 50 mol of urea is added per 1 mol of the rare earth element, and further 1 of the rare earth element is added.
A substance containing 0.01 to 0.2 mol of sulfate ion per mol is added, and the mixture is heated at 90 ° C or higher for 1 hour or longer. The generated precipitate is filtered, washed with water, and then calcined at 700 to 900 ° C for about 1 hour.
By this method, spherical rare earth element oxides having an average particle size of 2 to 10 μm can be obtained. As the salt of the rare earth element, chloride, nitrate, acetate or the like is used. Various substances can be used as the substance containing a sulfate ion, but when a metal ion in a product is not desired, sulfuric acid or ammonium sulfate is used. If the amount of the sulfate ion is less than 0.01 mol per mol of the rare earth element, no effect is obtained, and if it exceeds 0.2 mol, it is not preferable when the residual sulfur in the oxide is particularly disliked. If the heating temperature is 90 ° C. or the heating time is less than 1 hour, the reaction becomes insufficient and the precipitation yield becomes poor. The scope of application of the present invention is L containing Y as a rare earth element.
It is one element selected from a, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu, or a mixture of two or more elements.

[0006]

EXAMPLES The embodiments of the present invention will be described below with reference to examples, but the present invention is not limited thereto. (Example 1) 1 L of 0.05 mol / L yttrium chloride aqueous solution
To this, add 30 g of urea and 0.65 g of ammonium sulfate and dissolve completely. This solution was placed in a three-necked round-bottomed flask equipped with a stirrer, a reflux condenser and a thermometer.
Heated to ° C. Hold at about 100 ° C. for 2 hours. After cooling in a water bath, filter with a Buchner funnel, and use 500 ml of pure water each time.
It was sprinkled and washed. After air-drying the obtained precipitate,
It was baked at 00 ° C for 2 hours to obtain 5.50 g of yttrium oxide. This oxide was composed of spherical particles and had an average particle diameter of 4.5 μm as measured by the laser diffraction scattering method.

(Example 2) 8.90 g of gadolinium oxide was obtained by the same steps and conditions as in Example 1 except that 1 L of a 0.05 mol / L gadolinium chloride aqueous solution was used in place of the yttrium chloride aqueous solution. This oxide consists of spherical particles,
The average particle size measured by the laser diffraction scattering method was 4.7 μm.

(Comparative Example) The same treatment as in Example 1 was carried out except that the addition of ammonium sulfate was omitted to obtain 5.52 g of yttrium oxide. This oxide was composed of spherical particles and had a median particle diameter of 0.62 μm as measured by the laser diffraction scattering method.

[0009]

Industrial Applicability According to the present invention, it is possible to obtain a rare earth element oxide composed of spherical particles having a relatively coarse particle size by an extremely simple method, and its industrial utility value is extremely high such as for phosphor raw materials.

Claims (1)

[Claims] 1. A method for producing a rare earth element oxide, which comprises adding urea to an aqueous solution of a salt of a rare earth element containing a sulfate ion, heating the mixture, and calcining a precipitate formed therein.