Calcium Tungstate X-ray Phosphors and Method for Preparing Same

A calcium tungstate X-ray phosphor is disclosed which consists essentially of a calcium tungstate host and from about 50 to about 200 parts per million, based upon the weight of the host, of vanadium as a dopant. The disclosed phosphor exhibits no detectable lag or persistence and is appreciably brighter than prior X-ray phosphors. A process for producing the phosphor is also disclosed which process comprises forming an aqueous reaction media of a water-soluble calcium source and a water-soluble tungstate source having an excess of calcium, maintaining a temperature of above about 80°C for a time sufficient to form solid calcium tungstate having a stoichiometric excess of calcium, separating the solid calcium tungstate, adding from about 50 to 200 ppm of a vanadium source and a fluxing material, heating said calcium tungstate to a temperature of between about 700°C and 1150°C for a sufficient time to form a phosphor composition and washing the phosphor with sufficient water to remove any residual water soluble contaminants. An optional process is to add, in addition to the vanadium source, from about 0.05% to about 1.0%, based upon the weight of the host, of tungsten trioxide.

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