Theoretical and experimental study of polycrystalline phases obtained by the nanometric ZnTiO3 powder sintering

Abstract

In this study we have combined two research methods: structure prediction of ZnTiO3 using computational SPuDS software, and the characterization of binary oxides obtained from ZnO TiO2 system. Pure nanosized ZnTiO3 (99.5%), was compacted in cylindrical shape specimens by uniaxial double sided compaction and then sintered in air atmosphere in a dilatometric device [1,2]. One compact was sintered up to 915 °C to retain metastabile ZnTiO3 and held 5 minutes on that temperature, and another one at the same conditions, but now up to 970 °C to induce phase transition and to obtain stabile Zn2TiO4 and TiO2 according to phase diagram [2]. Reheated samples obtained at different characteristic temperatures in air were analyzed by X-ray diffraction (XRD). The infrared attenuated total reflectivity measurements confirmed XRD results. In order to estimate theoretical stability of these perovskite structure, Goldschmidt tolerance factor Gt and global instability index GII were calculated. Furthermore, the Ti valence states were determined by bond valence calculations (BVC). Also, we have investigated the formation of new phases (Zn2Ti3O8, TiO2 and Zn2TiO4) originating from ZnTiO3 with temperature change, as well as the relation between the crystal structures which have been predicted and the structure of the phases we have experimentally observed.