Rare earth oxide and its manufacturing method

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PROBLEM TO BE SOLVED : To produce a rare earth oxide having a small Fischer diameter, a large specific surface area and a small crystallite size and useful as a material of rare earth element-contg. ceramics, a sintering aid of ceramics, etc., by a profitable method comprising simple steps. SOLUTION : Ammonium hydrogencarbonate is added in a process for forming a precipitate by adding an alkali to an aq. soln. of a salt of a rare earth element and the resultant cake is separated by solid-liquid separation and fired at 300-900 deg.C to produce the objective rare earth oxide having =30 m2/g specific surface area and <=250 Å crystallite size.