Improvements in and relating to luminescent powders, and methods of manufacturing the same

Abstract

Abstract 521,099. Luminescent materials. BRITISH THOMSON-HOUSTON CO., Ltd., ANDERSON, J. T., and WELLS, R. S. Nov. 7, 1938, No. 32239. [Class 39 (i)] To render free flowing luminescent powders such as the sulphides of zinc and/or cadmium and/or manganese a gelatinous, semi-gelatinous, amorphous or finely crystalline powder is precipitated on the luminescent material ; the powder comprises oxides or hydroxides of chromium, beryllium, tin, magnesium, cadmium, cobalt, silicon, manganese, nickel, iron and/or silver or the phosphates where precipitable of the elements of groups II and III of the periodic table. The precipitation may be effected by ammonium hydroxide with a salt of the elements separately enumerated ; or by a soluble phosphate with a basic radicle giving an insoluble phosphate. The precipitation may be obtained by heat, addition of an electrolyte &c. In the case of silicon a colloidal solution of silica in alcohol is used the precipitation being effected by water. Dyes or pigments or chromium or iron hydroxides &c. may be added to colour the powders. Specification 511,038 is referred to.

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