BiFeO3 ceramics synthesized by spark plasma sintering

Phase-pure BiFeO3 particles were synthesized by an improved solid state technique. High density BiFeO3 ceramics were prepared using these particles by spark plasma sintering (SPS). The dielectric permittivity and loss of SPS samples were measured as functions of sintering temperature, frequency, and annealing conditions. Dielectric spectra of the ceramics annealed at 650 °C were characterized in a broad range of temperature (300–725 K) and frequency (100 Hz to 20 MHz). Two kinds of dielectric relaxation following the Arrhenius law were detected in low and high temperature ranges, respectively. The low temperature dielectric relaxation could be almost completely removed by annealing in vacuum and it should be assigned to be a valence fluctuation of Fe ions, while the high temperature dielectric relaxation was proposed to stem from the short-range motion of oxygen vacancies.