Abstract: A process for preparing a divalent europium activated alkaline earth metal aluminate phosphor represented by the composition formulaaMgO.multidot.bBaO.multidot.cAl.sub.2 O.sub.3 .multidot.dEuOwherein a, b, c and d satisfy the conditionsa+b+c+d=10, and0<a.ltoreq.2.00, 0.25.ltoreq.b.ltoreq.2.00, 6.0.ltoreq.c.ltoreq.8.5, 0.05.ltoreq.d.ltoreq.0.30. A magnesium compound easily alterable to MgO at a high temperature, barium halide or mixture of barium compounds easily alterable to BaO at a high temperature containing barium halide at such a rate that the amount of barium contained in the barium halide is not less than 70% by weight of the total amount of barium in the mixture of the barium compounds, an aluminium compound easily alterable to Al.sub.2 O.sub.3 at a high temperature and a europium compound easily alterable to Eu.sub.2 O.sub.3 at a high temperature are mixed at a mixing weight ratio to satisfy the above composition formula. The mixture thus obtained is fired in air at a temperature of 1200.degree.

Abstract: In an air-tight at least partially transparent container, a phosphor, a gas or gas mixture and a pair of discharging electrodes are contained. The discharge gap is in the range of 0.1 to 3.0mm, and the pressure of the gas or gas mixture sealed in the container is such that the product of the pressure and the discharge gap is in the range of 30 to 300 Torr.mm. The gas or gas mixture has discharge radiation spectra within the region of wavelength shorter than 200nm. The phosphor is a manganese activated aluminate phosphor represented by the formula(M.sup.II.sub.1-x, Mn.sub.x ) O.multidot.zAl.sub.2 O.sub.3where M.sup.II is selected from a group consisting of calcium, strontium, barium, magnesium and zinc, and x and z are numbers within the ranges of 10.sup.-3 .ltoreq.x.ltoreq.7.times.10.sup.-1 and 1.ltoreq.z.ltoreq.20, respectively.

Abstract: In an air-tight container made of transparent material, a phosphor, a gas or gas mixture and a pair of discharging electrodes are contained. The discharge gap is in the range of 0.1 to 3.0mm, and the pressure of the gas or gas mixture sealed in the container is such that the product of the pressure and the discharge gap is in the range of 30 to 300 Torr.mm. The gas or gas mixture has discharge radiation spectra within the region of wavelength shorter than 200nm. The phosphor is a europium activated yttrium gadolinium borate phosphor represented by the formula{ [ ( Y.sub.1-x, Gd.sub.x ).sub.1-z B.sub.z ].sub.1-y Eu.sub.y }.sub.2 O.sub.3where x, y and z are defined by the ranges of 0.ltoreq.x.ltoreq.1, 0.001.ltoreq.y.ltoreq.0.1 and 0.25.ltoreq.z.ltoreq.0.75. More preferably, x, y and z are defined by the ranges of 0.10.ltoreq.x.ltoreq.0.60, 0.005.ltoreq.y.ltoreq.0.05 and 0.50.ltoreq.z.ltoreq.0.65.

Abstract: A luminous device includes a cell, electrodes having a discharge gap of from 0.1 to 3.0 mm, a phosphor and a gas at a pressure of 30 to 300 nm, the gas having discharge emission spectra below 200 nm. The phosphor is one of various cerium activated yttrium silicates or europium activated orthophosphates and is disposed in the cell for exposure to the emission discharge of the gas. The device gives off blue light with higher emission efficiency and chroma saturation.