Crystal structure and fluorescence of compounds Ln 2Me 4+Me 6+O 8

Abstract

The crystal structures of compounds Ln 2Me 4+Me 6+O 8 are reported (Ln = La, GD, Y or Lu; Me 4+ = Si, Ge or Ti; Me 6+ = Mo or W). Nearly all of these compounds have the scheelite structure or the fergusonite (distorted scheelite) structure. A remarkable exception is Y 2SiMoO 8, which has zircon structure. In this compound the Si 4+ and Mo 6+ ions are long-range ordered. The fluorescence of the Eu 3+ ion in these host lattices was also investigated. The super structure of Y 2SiMoO 8 was confirmed by the spectral energy distribution of the Eu 3+ ion in this lattice. The emission spectra of the scheelites point to a considerable degree of order in the case of Me 4+ = Si. The low efficiency of the fluorescence is discussed. The fluorescent of the unactivated host lattices and of Bi 3+ and Tb 3+ ions in these lattices is dealt with.