Synthesis, microstructural characterization, and dielectric properties of BiFeO3 microcrystals derived from molten salt method

In this work, we report on the synthesis of BiFeO3 microcrystals by a facile molten-salt technique with the mixed medium of NaCl–KCl as the molten salt. The microstructures of BiFeO3 microcrystals were characterized by X-ray diffraction, Raman spectra, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The results show that almost pure phase BiFeO3 powders with the average particle size of 1.0 μm were synthesized at temperatures of 700–800 °C. However, the prolonged holding time and the change of molten salt ratios with respect to the starting oxides have no remarkable effects on the size and morphology of the BiFeO3 powders. Raman spectra of the BiFeO3 multiferroic ceramics prepared by the BiFeO3 microcrystals derived from the molten-salt method, reveal five Raman peaks at around 125, 145, 212, 268, and 504 cm−1. With increasing sintering temperature, the Raman peak at 145 cm−1 disappeared, a slight blue frequency shift was observed in the Raman peak at 212 cm−1, but no frequency shift was observed in the Raman peaks at around 125, 268, and 504 cm−1. The dielectric constants of the BiFeO3 multiferroic ceramics prepared from the BiFeO3 microcrystals synthesized by the molten-salt method, are in the range of 60–250 (measured @103 Hz and room temperature), and the corresponding dielectric losses are in the range of 0.05–0.2, which are dependent upon the molten-salt processing parameters.