GB684568A - Improvements in fluorescent materials - Google Patents

Abstract

684,568. Luminescent materals. THORN ELECTRICAL INDUSTRIES, Ltd. March 5, 1951 [March 14, 1950], No. 6433/50. Class 39(i) A luminescent material is prepared by heating a mixture of one or more phosphates of one or more of the metals calcium, strontium, barium, zinc and cadmium, one or more of the fluorides of said metals with or without a smaller quantity of a chloride, a compound or compounds of the actuating silver or silver plus manganese, the proportions of metal phosphorus and halogen being such that the ratio of metal atoms to phosphorus atoms is between 50:50 and 50:30, the ratio of metal plus phosphorus atoms to halogen lying between 1:0.05 and 1:0.5, the silver content being between 0.01 per cent and 5 per cent and the mangariese content if present not exceeding 10 per cent, both by weight. The chance of forming oxy- or hydroxy-apatite is reduced to a minimum. Heating is at 700‹-1300‹C. Calcium monohydrogen phosphate is prepared from calcium chloride and diammonium hydrogen phosphate and is mixed with calcium carborate, calcium fluoride and silver chloride and heated at 1150‹C. Manganese chloride may be added, and strontium fluoride may replace part of the calcium fluoride. The calcium in the above ingredients may similarly be replaced by barium or strontium, and part of these by zinc or cadmium. The metallic monohydrogen phosphate and the metal carbonate may be replaced by compounds of the metals which yield the oxides on heating and an ammonium phosphate. The silver is introduced as chloride, nitrate, sulphate or phosphate, and the manganese as phosphate, sulphate, fluoride or chloride.