Rare earth oxide powder and method for the preparation thereof

Details Rare earth oxide powder and method for the preparation thereof Rare earth oxide powder and method for the preparation thereof

1993-05-10

1994-07-26

Lewis, Michael

Chemistry of inorganic compounds

Treating mixture to obtain metal containing compound

Rare earth metal

423263, 534 16, C01F 1700, C07F 500

Patent

active

053325583

ABSTRACT:
An improved method is proposed for the preparation of a powder of rare earth oxide of which the particles have a predominantly polyhedral configuration with a relatively large particle size to be suitable, for example, as a host of phosphors. The method comprises the steps of (a) precipitating a rare earth ammonium oxalate by the admixture of an aqueous solution of a rare earth salt and ammonium oxalate, (b) separating the precipitates from the aqueous medium, (c) washing the same with deionized water to be freed from electrolytes, (d) dispersing and keeping the precipitates in a hot water bath at 50.degree. C. or higher for at least 15 minutes, (e) collecting the precipitates and (f) calcining the precipitates of the rare earth ammonium oxalate into oxide. It is essential that the steps (a) to (c) are conducted at a temperature of 40.degree. C. or below or, preferably, 30.degree. C. or below. The thus obtained precipitates of rare earth ammonium oxalate has a unique crystallographic structure not reported in any literatures, which, however, is a metastable phase gradually transformed into the known crystallographic structure.

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