Optical and crystallographic study of Eu3+ and Tb3+ doped LiYO2: Phase transition, luminescence efficiency and crystal field calculation

Crystallographic and optical studies were undertaken on powder samples of LiYO2 doped with Eu3+ and Tb3+. At room temperature, the compounds are monoclinic. A slight rise of the temperature or small quantities of a smaller cation (Tb4+) induces a phase transition to a tetragonal form. The radiant efficiencies are 0.33 and 0.47 those of the commercial red and green TV standards Y2O2S:Eu3+ and ZnS:Cu,Al, respectively. While stable at room temperature, the compounds do decompose into the oxides as the temperature is raised above 250 degrees C. The F-7 multiplet and the lowest D-5 energy levels of the Eu3+ (4f(6)) and the Tb3+ (4f(8)) configurations are determined. Experimentally fitted crystal field parameters are compared to predicted parameters. (C) 1996 Academic Press, Inc.