GB495706A - Improvements in combinations of a source of radiation with material adapted to be excited to luminescence by the radiation - Google Patents

Abstract

495,706. Luminescent materials. GENERAL ELECTRIC CO., Ltd., McKEAG, A. H., and RANDALL, J. T. April 16, 1937, Nos. 10922/37 and 1194/38. [Class 98 (i)] A luminescent material contains as essential elements cadmium, manganese, chlorine, phosphorus and oxygen in proportions to yield a crystal structure in which the unit cell is hexagonal and has axes a‹ = 9À 7A. U. and Co = 6À4A.U. Two alternative methods of preparation are described using materials known under the Registered Trade Mark " Analar," and each includes a common step. In this step, 480 gm. of cadmium sulphate is dissolved in 1500 ml. of boiling distilled water, and 160 grams of di-ammonium hydrogen orthophosphate is dissolved in 1000 ml. of boiling distilled water. 10 ml. of the second solution is added to the first solution, the precipitate filtered and discarded, the remainder of the second solution added, the precipitate filtered, washed well, and dried at 180‹ C. for three hours. The resultant is precipitate A. In the first method a solution of manganous chloride is added to precipitate A to form a paste, dried and heated in air at 925‹ C. for half an hour. It is then washed in hot distilled water and dried at 180‹ C. for 2 hours. In the second method 370 gms. manganous sulphate are dissolved in 1500 ml of boiling distilled water and 160 gms. di-ammonium hydrogen phosphate in 1000 ml. of water, the solutions mixed, and the precipitate washed and dried. This precipitate (precipitate B) is mixed with precipitate A and ordinary commercial cadmium chloride in proportions 5, 100 and 20 respectively. The substances are ground and mixed, and heated in a tubular boat at 800‹ C. for half an hour. The luminescence excited by radiation of wave length 2200-2600 ranges from orange yellow to pink. Increase in the content of manganese has the effect of increasing the excitation by the mercury line 3650 A.U. The proportion of manganese in the material may vary from 1 per cent to 20 per cent. The material may be combined with a high pressure mercury vapour discharge lamp having a quartz envelope, and may be mixed with luminescent materials which give a blue light. The applications to low pressure mercury discharge lamps and to cathode-ray tubes in conjunction with willemite are also described. Specifications 457,486, 469,731, and 473,715 are referred to.