Abstract: The invention contemplates a highly solar-energy absorbing device wherein the surface exposed to incident solar energy is a particularly characterized roughness of an amorphous semiconductor material, the particular characterization being that of an array of outwardly projecting structural elements of relatively high aspect ratio and at effective lateral spacings which are or include those in the order of magnitude of wavelengths within the solar-energy spectrum.

Abstract: Two new barium magnesium fluorides, Ba.sub.2 Mg.sub.3 F.sub.10 and BaMg.sub.3 F.sub.8, can be prepared by solid state reactions of barium fluoride and magnesium fluoride by heating in controlled atmospheric conditions at a temperature from about 700.degree. C to about 850.degree. C. In the BaF.sub.2 -MgF.sub.2 binary system, compositions containing from about 40 to 85 mole percent of MgF.sub.2 when activated by europium alone or in combination with manganese have been found to luminesce when excited by ultraviolet light, cathode rays, or with x-ray bombardment. Lamps incorporating these materials afford benefits of high temperature stability and x-ray intensifying screens incorporating these materials yield a speed equal to or better than present screens employing calcium tungstate.

Abstract: In europium-activated alkaline earth fluorohalide x-ray phosphors, the brightness is improved by having a detectable amount of the europium activator in the trivalent state. This beneficial effect is achieved by using a non-reducing firing atmosphere during synthesis for a sufficient time to produce an amount of trivalent europium that is detectable by exciting a sample of the phosphor after firing with 254 nanometer excitation.

Abstract: An x-ray luminescent phosphor composition consists essentially of a europium activated barium fluorochloride and an effective amount of brightness enhancement additive selected from lead, thallium and aluminum ions. The compositions are prepared by a solid state process in which a barium chloride and barium fluoride and a europium source are heated together in a non-oxidizing atmosphere with a source of lead or thallium or aluminum hydroxide. The temperatures utilized are from about 750.degree. to 925.degree.C for from about 1 to about 24 hours.