Haloapatite phosphors in the form of spherical particles and method of making same

Abstract

Abstract Alkaline earth haloapatite phosphors are provided in the novel form of substantially spherical particles, having diameters between about 1 and 20 microns. Haloapatite phosphor particles having this configuration are prepared by spray drying a semicolloidal suspension of precipitated haloapatite crystallites. Such a suspension is prepared by reacting aqueous solutions containing the constituent ions of an alkaline earth halophosphate. Desirably, the reaction solution is digested at about 60* C. and filtered to remove the precipitate which is then washed and reslurried to provide the suspension which is fed to the spray dryer. Activators such as antimony and manganese are normally incorporated in the phosphor by including ions of such activators in the reactant solutions. Fluorescent properties of the dried spherical phosphor are fully developed by brief thermal refining at about 1,050* to 1,200* C. Spherical phosphor particles are more readily dispersible in the usual coating media than are the irregular phosphor particles known heretofore. Because of their ability to pack together more closely and have a lesser void fraction, spherical phosphors provide fluorescent lamp coating of improved uniformity and greater optical density.

Inventors

• 👤 L Pitt
• 👤 J Starbuck

Bibliographic Details