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Luminescence of Eu2+ in Barium and Strontium Aluminate andGallate.-The Eu2+ luminescence of the title compounds Ba1-xSrxAl2-yGayO4 (x: 0, 0.5, 1 and y: 0, 1, 2) of stuffed tridymite structure is studied. Green luminescence is observed in the Eu2+ doped Ba and Sr aluminates from Eu2+ on the two different alkaline earth sites in the lattice of these compounds. Due to the preferential orientation of a d orbital of Eu2+ on the Ba or Sr sites, the Eu2+ luminescence is at low energy. The absence of Eu2+ luminescence in BaGa2O4:Eu2+ and SrGa2O4:Eu2+ is attributed to photoionization. In BaAlGaO4:Eu2+ and SrAlGaO4:Eu2+ the luminescence behavior of Eu2+ is comparable to that of BaAl2O4:Eu2+ and SrAl2O4:Eu2+ but exhibits a lower efficiency. -(POORT, S. H. M.; BLOKPOEL, W. P.; BLASSE, G.; Chem. Mater. 7 (1995) 8, 1547-1551; Debye Inst., Utrecht Univ., NL-3508 TA Utrecht, Neth.; EN)