JPH07309622A - Method for producing fine powder of rare earth element oxide - Google Patents

Abstract

(57) [Summary] (Revised) [Purpose] To provide a fine powder of rare earth element oxide having a narrow particle size distribution, which is useful as a ceramics sintering aid and the like. [Structure] A precipitate obtained by mixing an aqueous solution of a water-soluble rare earth element compound with citric acid and a base is heated to 600 ° C or more in the atmosphere.
A method for producing fine powder of rare earth element oxide, which is fired at 1500 ° C or lower.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mainly relates to a method for producing a fine powder of rare earth element oxide which is useful as a ceramics sintering aid.

[0002]

2. Description of the Related Art It is known that rare earth element oxide fine powder is obtained by firing a rare earth element ammonium oxalate double salt, carbonate or the like.

[0003]

Some rare earth element oxide fine powders obtained by the conventional method have an average particle size of about 1 μm, but the particle size distribution is tailed toward the large particle size side. When observed under an electron microscope, many particles are aggregated with each other. On the other hand, as a ceramics sintering aid,
Ideally, a monodisperse powder is considered to be good, and in the case of a conventional rare earth element oxide fine powder, it is considered that considerable energy is required to uniformly mix even the fine region of the ceramic base material. The present invention solves such a drawback, and an object thereof is to provide a fine powder of a rare earth element oxide which is a fine particle and has a narrow particle size distribution and which can be uniformly mixed with a ceramic main agent.

[0004]

In order to solve the above problems, the present inventors have studied the formation of precipitates of rare earth elements by various organic acid salts, and as a result, precipitated and burned citrate under specific conditions. In this case, it was found that a rare earth element oxide fine powder having a sharp particle size distribution close to monodisperse was obtained, and the present invention was completed by establishing various conditions, the gist of which is an aqueous solution of a water-soluble rare earth element compound, This is a method for producing a fine powder of rare earth element oxide, in which a precipitate obtained by mixing citric acid and a base is fired in the air at 600 ° C. or higher and 1500 ° C. or lower.

The present invention will be described in detail below. chloride,
To an aqueous solution of a water-soluble rare earth element compound having a concentration of 0.01 to 0.5 mol / L such as nitrate, there is added about 1 mol of citric acid per 1 mol of the rare earth element and a base sufficient to neutralize the acidic carboxyl group of citric acid. At this time, the amount of citric acid is preferably about 1 mol per 1 mol of the rare earth element, and if the amount is too large or too small, the yield will be poor. Ammonia as base,
Examples thereof include inorganic bases such as alkali hydroxide, and organic bases such as hexamethylenetetramine and triethanolamine, and ammonia or an organic base is preferable when mixing of alkali metal into the product is not desired. Further, instead of adding citric acid and a base separately, a part or all of them may be added as a salt of citric acid (regular salt or acidic salt). Further, the higher the mixing temperature is, the better the yield tends to be, but if the temperature is higher than 60 ° C, the effect is small. The precipitate produced as described above is filtered, washed with water and dried if necessary, and then calcined in an electric furnace at 600 ° C. or more and 1500 ° C. or less in the atmosphere to obtain fine powder of rare earth element oxide. The applicable range of the present invention is La, Ce, P containing Y as a rare earth element.
r, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and L
It is one element selected from u or a mixture of two or more elements.

[0006]

EXAMPLES The embodiments of the present invention will be specifically described below with reference to examples, but the present invention is not limited thereto. Example 1 700 ml of an aqueous solution of yttrium nitrate having a concentration of 0.3 mol / L and a pH of 2.0 was placed in a beaker and heated to 50 ° C. in a water bath while stirring at about 200 rpm. Diammonium citrate 47.5g, ammonia water (concentration 15mol / L) 14
ml and 140 ml of water were added and the solution was added over 5 minutes with continuous stirring. After continuing stirring for further 10 minutes, the mixture was filtered with a Buchner funnel, sprinkled with 1200 ml of water at about 40 ° C., and washed. The cake thus obtained was placed in a porcelain crucible, placed in an electric furnace, and baked in the air at 800 ° C. for 1 hour. 23.2 g of yttrium oxide was obtained. As a result of measuring the particle size distribution of this oxide by a laser diffraction method, n volume% of all particles was φ n (particle size
(φm)), the definition of φ n is
φ50 was 0.94 μm and φ90 was 2.06 μm. Further, when observed with an electron microscope, it was composed of well-dispersed scaly particles having a length of 0.6 to 0.9 μm.

(Example 2) In place of an aqueous solution of citric acid and ammonia, a solution prepared by previously mixing 44.2 g of citric acid monohydrate, 94.0 g of triethanolamine and 100 ml of water was added. In the same manner as in Example 1, 23.2 g of yttrium oxide was obtained. The particle size distribution by the laser diffraction method was 50, 0.96 μm, and 90, 2.09 μm, and the appearance observed with an electron microscope was the same as in Example 1.

(Comparative Example) Instead of an aqueous solution of citric acid and ammonia, 53.0 g of oxalic acid, aqueous ammonia (concentration 15 mol / L
23.3 g of yttrium oxide was obtained in the same manner as in Example 1 except that a solution prepared by previously mixing 56.0 ml and 310 ml of water was added. Φ50 of particle size distribution by laser diffraction method is
1.18 μm and φ90 were 2.90 μm, and when observed by an electron microscope, each particle was a plate-like particle of about 0.5 μm, but 2 to 10 or more aggregated particles were conspicuous.

[0009]

EFFECTS OF THE INVENTION According to the present invention, it is possible to provide a fine powder of a rare earth element oxide which is a fine particle and has a narrow particle size distribution and which can be uniformly mixed with a ceramic main agent, and is useful mainly as a ceramics sintering aid. Its utility value is extremely high.

Claims (1)

[Claims] 1. A precipitate obtained by mixing an aqueous solution of a water-soluble rare earth element compound, citric acid and a base, at 600 ° C. in the atmosphere.
A method for producing a fine powder of rare earth element oxide, which comprises firing at 1500 ° C. or lower.