PURPOSE: To coat the hydroxide or oxide of metal on the surfaces of micro powder particles to a uniform thickness by suspending the powder particles in a benzene soln. of te alkoxide of the metal to be coated then adding water to hydrolyze the same and calcining the particles after drying.

CONSTITUTION: The coating of Pb on the surfaces of pulverized powder particles of PLZT having, for example, 500W1,000 grain sizes is accomplished in the following way: A benzene soln. of alkoxide of PbO is prepd. and the pulverized powder of PLZT is suspended thereon. Distilled water is added to the suspension which is then hydrolyzed under stirring. The resulted precipitate is filtered and is dried, then the dried precipitate is calcined at, for example, 500°C. As a result, the Pb is coated on the surfces of the micro particles to a uniform thickness by the relatively simple stage. (a)W(c) in the figure are the schematic diagram showing the state of the powder particles in the treatment stage.