Microstructure and luminescence of Eu-doped Li1+x-yNb1-x-3yTix+4yO3 solid solutions with superstructure

Abstract

Eu doped Li-Nb-Ti oxide (LNT) solid solutions were prepared by heating mixed powders at temperatures of 1120°C for up to 24 h. Despite the fact that these materials often possess a crystallographic superstructure, no such structure was observed for a sintering time of 10 h. For the longer sintering period of 24 h, no superstructure was observed for samples with less additions of TiO₂, but it was confirmed by X-ray diffraction and a High-Resolution Transmission Electron Microscopy that samples with compositions containing 20 and 25 mol%-TiO₂ did possess superstructures. Heating for 24 h resulted in an improvement of the photoluminescence (PL) intensity of the LNT solid solutions, and this increase was more marked in the samples where the superstructure was developed. For the Eu-doped LNT solid solution containing 25 mol%-TiO₂, the PL intensity of the sample with the superstructure was almost 3 times as high as that of a sample with the same doping but without the superstructure.