Bi volatilization and conduction mechanism of rapidly liquid phase sintering La-doped BiFeO3 perovskite ceramics

Abstract

LaxBi1−xFeO3 (LBFO) materials were synthesized by sol–gel method with x = 0.0, 0.1, 0.2, and 0.3. LBFO ceramics were obtained by rapid liquid phase sintering and conventional sintering, respectively. X-ray diffraction (XRD) and Raman spectroscopy indicated that the phase transition from twisted diamond R3C to orthogonal Pbnm occurs in the course of the increase of La element doping. Scanning electron microscopy demonstrated that the grain size of LBFO ceramics decreased from 10 to 1 μm, with the increase of La ion doping, and the volatilization of Bi decreases from 6.48 to 1.43%. It was found that LBFO ceramics have the characteristic of negative temperature coefficient (NTC), the resistivity (100 °C) is from 4.32 × 106 to 2.71 × 108 Ω cm, the material constant (B100/700 value) is about 6000–9000 K, the activation energy of LBFO is around 0.56 to 0.82 eV, and the temperature range of LBFO is from 100 to 700 °C. The resistivity change of LBFO is less than 1% after 500 h of ageing at 300 °C.