GB877536A - Improvements in or relating to the manufacture of phosphors - Google Patents

Abstract

877,536. Luminescent materials. GENERAL ELECTRIC CO. Ltd. March 4, 1958 [May 1, 1957], No. 13938/57. Divided out of 877,535. Class 39(1). A method of making a crystalline phosphor consisting of alkaline earth metal(s) halophosphate(s) activated by tin in the stannous state with or without copper in the cuprous state and with or without manganese, so as to be excitable by short or long wavelength U.V. radiation in low pressure or high pressure mercury vapour discharge lamps, cathode rays or X-rays, comprises mixing the halophosphate material, or a mixture of compounds which react to produce such material on heating, with a compound or compounds of tin with or without a compound or compounds of copper and with or without a compound of manganese, and heating the mixture in an applied weakly reducing atmosphere at a temperature or temperatures within the range of 700‹C. to 1250‹C. The proportion of tin or tin and copper, and of the manganese, is within the range of 0.001 to 5.0%, preferably 0.1 to 2.0%, by weight of the total weight of the phosphor, including the activator or activators, calculated from the starting materials used, The heating can be effected in at least two stages, the second and any subsequent heatings being preferably at a higher temperature than the first, and the material being ground between the heating steps. The applied weakly reducing atmosphere can be a mixture of nitrogen and hydrogen in a ratio within the range of 1000 N 2 :1 H 2 to 200 N 2 :1 H 2 , by volume, in the case of activation by tin and copper with or without manganese, or in a ratio within the range of 200 N 2 :1 H 2 to 100 N 2 :1 H 2 , by volume, in the case of activation by tin without copper and with or without manganese. Several specific examples are described. Specifications 580,363, 610,025 and 614,700 also are referred to.