Elektronenstrahlroehre mit einem Leuchtschirm

733,077. Luminescent materials. PHILIPS ELECTRICAL INDUSTRIES, Ltd. June 13, 1952 [June 16, 1951], No. 14944/52. Drawings to Specification. Class 39 (1). A high vacuum cathode-ray tube for use in apparatus for televising films or diapositives and in radar apparatus comprises a luminescent screen which contains a luminescent material which will emit radiation in the short-wave blue and long-wave ultra-violet parts of the spectrum, said material being activated by trivalent cerium and having a decay time of the fluorescence shorter than 10-6 sec., which material is a crystallized fired reaction product consisting solely of silicon, oxygen, one or more alkaline earth metals and, if desired, aluminium, said elements being present in such quantities that the material can be symbolically represented by a point within a specified domain in the ternary system M-SiO 2 -Al 2 O 3 , M representing the alkaline earth metals. The cerium content of the material is between 0.05 and 10 mol. per cent of the total quantity of alkaline earth oxide. Methods of preparing luminescent materials of the composition 2CaO.Al 2 O 3 .SiO 2 : 2 mol. per cent of trivalent cerium and 2SrO.Si0 2 : 2 mol. per cent of trivalent cerium are described. Specification 652,091 is referred to.