Luminescence properties of rare earth ions in polytantalate

The luminescence properties of R3+ (R3+=Eu3+, Tb3+, Tm3+) in La1-xRxTa7O19 solid solution were systematically examined. In this host lattice, the distance between nearest neighbors of the La3+ site which were substituted by the R3+ ions, were very long (about 0.62 nm) and the sites locate two-dimensionally. The critical concentration at which the concentration quenching occurred under UV excitation were x=1.0 in La1-xEuxTa7O19, x=0.9 in La1-xTbxTa7O19 and x=0.14 in La1-xTmxTa7O19. Furthermore the energy migration process of these samples were investigated. (C) 1998 Elsevier Science S.A.