Crystal structure stability of simulated Sr1–1.5x Y x TiO3 (x = 0–0.12) waste forms

Abstract

A series of Sr1–1.5xYxTiO3 (x = 0–12) solid solutions were synthesized by a solid state reaction process. The effects of reaction temperature and dopant on the crystallinity, microstructure and morphology of Sr1–1.5xYxTiO3 (x=0–0.12) were investigated. Pure and single-phase perovskite-type Sr1–1.5xYxTiO3 (x<0.08) solid solutions were obtained at 1 400 °C for 6 h. The perovskite-type SrTiO3 and pyrochlore-phase Y2Ti2O7 coexisted for x = 0.08–0.12, leading to an unstable and unfavourable solid solution structure for long-term immobilization of the 90Sr. The X-ray diffraction patterns for Rietveld refinement analysis confirmed the formation of a Sr1–1.5xYxTiO3 (x = 0–0.12) continuous solid solution. Stretching and bending vibrations were assigned in the infrared region. The SrTiO3 grain size increased with Y content. The leaching behavior of Y3+ from the waste forms of Sr1–1.5xYxTiO3 was controlled by its structural change.