Abstract: Luminescent alkaline earth metal orthosilicate activated by praseodymium, defined by the formula M.sub.2-3/2x-1/2y Pr.sub.x M'.sub.y SiO.sub.4 in which M is at least one of the elements Ca and Sr of which up to 50 mol % may be replaced by Ba and/or of which up to 20 mol % may be replaced by Mg, in which M' is at least one of the elements Li, Na and K and in which 0.004.ltoreq.x.ltoreq.0.10 and 0.ltoreq.y.ltoreq.0.10.

Abstract: Luminescent terbium-activated alkaline earth metal rare earth metal borate having a monoclinic crystal structure and being defined by the formula M.sub.3 Ln.sub.1-x Tb.sub.x (BO.sub.3).sub.3 in which M is at least one of the elements Ba, Sr and Ca of which up to 34 mol % may be replaced by Mg, in which Ln is at least one of the elements La, Gd, Y and Sc and in which 0.005.ltoreq.x.ltoreq.1.

Abstract: A luminescent screen provided with a luminescent material having the hexagonal crystal structure, which material is an aluminate, a gallate or an aluminate gallate. The crystal structure of the luminescent material corresponds to that of at least one of the compounds .beta.-aluminium, .beta."-alumina and the hexagonal ferrites. The luminescent material is activated by at least one of the elements manganese, europium, lead, thallium, cerium, indium, terbium, dysprosium and bismuth and is a ternary compound whose composition can be represented in the ternary phase diagram ABC in which A represents at least one of the oxides 1/4Na.sub.2 O, 1/2K.sub.2 O, 1/2Rb.sub.2 O, 1/2Cs.sub.2 O, CaO, SrO, BaO, 1/2La.sub.2 O.sub.3, 1/2Ce.sub.2 O.sub.3, 1/2Tb.sub.2 O.sub.3, 1/2Dy.sub.2 O.sub.3, 1/2Bi.sub.2 O.sub.3, EuO, PbO, 1/2Tl.sub.2 O and 1/2In.sub.2 O, in which B represents at least one of the oxides Al.sub.2 O.sub.3 and Ga.sub.2 O.sub.3 in which up to 25 mol. % of the oxides denoted by B may be replaced by Sc.sub.2 O.

Abstract: Luminescent Eu.sup.2+ activated barium-hexa-aluminate mainly having the crystal structure of .beta.'-alumina and being defined by the formula (x-p)BaO.pEuO.(6-0.67x)Al.sub.2 O.sub.3 in which 0.90.ltoreq.x.ltoreq.1.22 and 0.005.ltoreq.p.ltoreq.0.25 and in which 1 to 20 mol % of the BaO is replaced by at least one of the oxides CaO and 0.67Li=.sub.2 O, exhibits improved performance as a blue line emitter.

Abstract: Luminescent Eu.sup.3+ -activated alkaline earth metal-rare earth metal silicate, which is defined by the formulaBa.sub.2 Gd.sub.2-x-y Y.sub.x Eu.sub.y Si.sub.4-z Ge.sub.z O.sub.13,in which O.ltoreq.x.ltoreq.1.3, 0.01.ltoreq.y.ltoreq.1.0 and O.ltoreq.z.ltoreq.4, luminescent screen provided with such a silicate and low-pressure mercury vapor discharge lamp provided with such a screen.

Abstract: A luminescent screen provided with a terbium-activated silicate having a cuspidine crystal structure according to the formula Y.sub.4-x-z-p Ca.sub.x M.sub.z.sup.II Tb.sub.p Si.sub.2-y Al.sub.y O.sub.7+x+z+y N.sub.2-x-z-y. In this formula M.sup.II is at least one of the elements Mg, Sr and Ba. The yttrium can be replaced up to at most 50 mol. % by Gd and/or La. It further holds that:0.ltoreq.x.ltoreq.1.90.ltoreq.z.ltoreq.1.0o.ltoreq.y.ltoreq.1.9x+z+y.ltoreq.1.90.05.ltoreq.p.ltoreq.1.5.

Abstract: A luminescent screen provided with a zirconium- and/or terbium-activated silicate having an apatite crystal structure according to the formulaLn.sub.10-x-p-q M.sub.x.sup.II Tb.sub.p Zr.sub.q (SiO.sub.4).sub.6-y (M.sup.III O.sub.4).sub.y O.sub.x+y-q N.sub.2-x-y+q.In this formula, Ln is at least one of the elements Y, La and Gd. M.sup.II is Mg, Ca and/or Sr and M.sup.III is A1 and/or B. It further holds that:______________________________________ 0 .ltoreq. x .ltoreq. 1.9 0 .ltoreq. p .ltoreq. 3 0 .ltoreq. y .ltoreq. 1.9 0 .ltoreq. q .ltoreq. x + y x + y .ltoreq. 1.9 0.1 .ltoreq. p + q.

Abstract: A luminescent screen provided with a luminescent material having the hexagonal crystal structure, which material is an aluminate, a gallate or an aluminate gallate. The crystal structure of the luminescent material corresponds to that of at least one of the compounds .beta.-aluminium, .beta."-alumina and the hexagonal ferrites. The luminescent material is activated by at least one of the elements manganese, europium, lead, thallium, cerium, indium, terbium, dysprosium and bismuth and is a ternary compound whose composition can be represented in the ternary phase diagram ABC in which A represents at least one of the oxides 1/4Na.sub.2 O, 1/2K.sub.2 O, 1/2Rb.sub.2 O, 1/2Cs.sub.2 O, CaO, SrO, BaO, 1/2La.sub.2 O.sub.3, 1/2Ce.sub.2 O.sub.3, 1/2Tb.sub.2 O.sub.3, 1/2Dy.sub.2 O.sub.3, 1/2Bi.sub.2 O.sub.3, EuO, PbO, 1/2Tl.sub.2 O and 1/2In.sub.2 O, in which B represents at least one the oxides Al.sub.2 O.sub.3 and Ga.sub.2 O.sub.3 in which up to 25 mol. % of the oxides denoted by B may be replaced by Sc.sub.2 O.sub.

Abstract: A luminescent screen provided with a luminescent material having the hexagonal crystal structure, which material is an aluminate, a gallate or an aluminate gallate. The crystal structure of the luminescent material corresponds to that of at least one of the compounds .beta.-aluminium, .beta."-alumina and the hexagonal ferrites. The luminescent material is activated by at least one of the elements manganese, europium, lead, thallium, cerium, indium, terbium, dysprosium and bismuth and is a ternary compound whose composition can be represented in the ternary phase diagram ABC in which A represents at least one of the oxides 1/4Na.sub.2 O, 1/2K.sub.2 O, 1/2Rb.sub.2 O, 1/2Cs.sub.2 O, CaO, SrO, BaO, 1/2La.sub.2 O.sub.3, 1/2Ce.sub.2 O.sub.3, 1/2Tb.sub.2 O.sub.3, 1/2Dy.sub.2 O.sub.3, 1/2Bi.sub.2 O.sub.3, EuO, PbO, 1/2Tl.sub.2 O and 1/2In.sub.2 O, in which B represents at least one of the oxides Al.sub.2 O.sub.3 and Ga.sub.2 O.sub.3 in which up to 25 mol. % of the oxides denoted by B may be replaced by Sc.sub.2 O.

Abstract: A luminescent screen provided with a luminescent material having the hexagonal crystal structure, which material is an aluminate, a gallate or an aluminate gallate. The crystal structure of the luminescent material corresponds to that of at least one of the compounds .beta.-aluminium, .beta."-alumina and the hexagonal ferrites. The luminescent material is activated by at least one of the elements manganese, europium, lead, thallium, cerium, indium, terbium, dysprosium and bismuth and is a ternary compound whose composition can be represented in the ternary phase diagram ABC in which A represents at least one of the oxides 1/4Na.sub.2 O, 1/2K.sub.2 O, 1/2Rb.sub.2 O, 1/2Cs.sub.2 O, CaO, SrO, BaO, 1/2La.sub.2 O.sub.3, 1/2Ce.sub.2 O.sub.3, 1/2Tb.sub.2 O.sub.3, 1/2Dy.sub.2 O.sub.3, 1/2Bi.sub.2 O.sub.3, EuO, PbO, 1/2Tl.sub.2 O and 1/2In.sub.2 O, in which B represents at least one of the oxides Al.sub.2 O.sub.3 and Ga.sub.2 O.sub.3 in which up to 25 mol. % of the oxides denoted by B may be replaced by Sc.sub.2 O.

Abstract: A luminescent beryllium-containing silicate activated by bivalent europium defined by the formula Me.sub.1-x Eu.sub.x Be.sub.a Si.sub.a O.sub.3a+1, in which 0.005 .ltoreq.x.ltoreq.0.20 and a has the value 1 or 2 and in which Me represents at least one of the alkaline earth metals barium, strontium and calcium. If a = 2 at least 50 gram-atomic % of Me is strontium. If a = 1 up to 25 gram.atomic % of Be together with the same quantity of Si may be replaced by an equiatomic quantity of Al.The luminescent silicate is preferably used in mercury vapor discharge lamps.