Study on Phase Stability of Hexagonal Ba(Ti0.95Fe0.05)O3-δ Ceramic via Temperature-Dependent X-Ray Diffraction

The crystalline structure of the hexagonal Ba (Ti0.95Fe0.05)O3−δ(BTF) ceramic were directly measured using a temperature-dependent XRD technique. Different from the traditional structural transitions of rhombohedral-orthorhombic (−90 °C), orthorhombic-tetragonal (−10 °C), and tetragonal-cubic (i.e., the Curie temperatureTC= 130 °C) for BaTiO3, the phase transition from hexagonal to any phase above for BTF cannot occur atTCeven up to 300 °C. Increasing temperature cannot give rise to the occupation of oxygen vacancies by environmental oxygen absorbed. The lattice electro-neutrality maintained by Fe3+-VO-Fe3+defect complexes is predominant in BTF. This experiment clarifies the phase stability of the hexagonal perovskite structure aboveTCup to 300 °C.