Abstract: Luminescent alkaline earth metal silicate aluminate defined by the formula Sr.sub.3-a-b Ba.sub.a Ca.sub.b Si.sub.1-y Ge.sub.y Al.sub.10-z Ga.sub.z O.sub.20 ; Ce.sub.p.sup.3+, Eu.sub.q.sup.2+, Tb.sub.r.sup.3+, wherein, if r=0, it holds that0.ltoreq.a+b.ltoreq.1.50.ltoreq.p.ltoreq.0.750.ltoreq.q.ltoreq.0.250.001.ltoreq.p+qand wherein, if p+q=0, it holds that0.ltoreq.a.ltoreq.3.00.ltoreq.b.ltoreq.1.5a+b.ltoreq.3.00.01.ltoreq.r.ltoreq.1.0.The material is used in a luminescent screen, preferably in the luminescent screen of a low-pressure mercury vapor discharge lamp.

Abstract: Luminescent material having a host lattice comprising, as one of the main constituents, at least one of the elements Y, La and the lanthanides. The material is activated by Gd, and, in addition by one or more of the elements Pb, Tl, Sb, Pr and Bi and comprises one or more of the elements Mn, Tb, Eu, Dy and Sm and the third activator. These materials have an efficient emission originating from the third activator and are used in low-pressure mercury vapour discharge lamps.