Patent ID: 6132642
Filing Date: 2000-10-17
Classification: C09K,G01N

Abstract:
A process for the preparation of small particle size spherical phosphor particles which comprises:a) preparing an aqueous solution of soluble salts of a rare earth phosphor-precursor metal in amounts required to make a phosphor and an organic chemical that releases hydroxyl ions by hydrolysis;b) precipitating rare earth hydroxycarbonate particles from said solution, said particles having a spherical shape and particle size of less than one micron;c) collecting the rare earth hydroxycarbonate particles;d) heating the hydroxycarbonate particles in an oxygen-containing atmosphere at a temperature in the range of about 700 to about 1000.degree. C. to form the corresponding rare earth oxide compound while maintaining the particle size and spherical shape of the hydroxycarbonate particles; ande) heating the rare earth oxide particles in a flux composition of sulfur and one or more salts selected from the group consisting of alkali metal sulfates, phosphates and carbonates in the absence of oxygen at a temperature of no more than about 900.degree. C. to convert the oxide to the corresponding oxysulfide compound without changing the shape or the particle size of the particles.