On the luminescence of Ba5M4O4O15 (M = Ta5+, Nb5+)

The low-temperature luminescence properties of the perovskite-derived materials, Ba5M4O15 (M = Ta5+, Nb5+) are reported and discussed. The octahedrally coordinated tantalate groups of Ba5Ta4O15 exhibit a blue emission, whereas the niohate groups in Ba5Nb4O15 luminesce yellow upon excitation with short wavelength ultraviolet radiation, The low quenching temperatures of the tantalate and niobate luminescence are a result of energy migration to quenching sites in the host lattice, The luminescence characteristics of Ba5Ta4O15 and Ba5Nb4O15 are compared with those reported for other perovskite-based tantalates/niobates and the results are discussed in terms of electronic delocalization of the excited nd(0) configuration. (C) 1997 Academic Press.