Firing and milling method for producing a manganese activated zinc silicate phosphor

Abstract

Abstract A method for producing manganese activated zinc silicate phosphor wherein the individual phosphor particles are surrounded with a non-particulate, conformal aluminum oxide coating is disclosed. The method comprises dry blending a mixture of components consisting essentially of zinc oxide, silicic acid, a source of manganese, ammonium chloride, ammonium fluoride, tungstic oxide, and silica, wherein the Zn+Mn/Si mole ratio is from about 1.95 to about 2.02, wherein the silica is colloidal and has a surface area of from about 50 to about 410 m 2 per gram, and wherein the colloidal silica makes up from about 0.01% to about 1.0% by weight of the mixture; firing the resulting dry blend of components in a nitrogen atmosphere at a temperature of from about 1200° C. to about 1300° C. for a sufficient time to produce the phosphor; milling the resulting phosphor for a period of time of from about 60 minutes to about 120 minutes; firing the resulting milled phosphor in air at a temperature of from about 1175° C. to about 1275° C. for a sufficient time to diffuse the tungsten and manganese to the surfaces of the phosphor particles; applying a non-particulate, conformal aluminum oxide coating to the outer surface of individual particles of the phosphor while the phosphor particles are suspended in a fluid bed having a midpoint temperature between 400° and 480° C., the aluminum oxide coating being formed by a chemical vapor deposition reaction involving oxidation of trimethyl aluminum; and annealing the aluminum oxide coated phosphor for a period of time from 4-16 hours at a temperature between 750° and 800° C.

Inventors

• 👤 Anthony F. Kasenga
• 👤 A. Gary Sigai
• 👤 Thomas E. Peters
• 👤 Roger B. Hunt

Bibliographic Details