Pressure induced phase transition of La-substituted BiFeO3

Abstract

The structure of La doped BiFeO3, prepared by the conventional hydrothermal method, were investigated at room temperature using X-ray diffraction (XRD), X-ray absorption fine structure (XAFS) spectroscopy. The XAFS spectra showed that La in fact substitute the Bi site of secondary nanosized particles with orthorhombic symmetry instead of the long-believed rhombohedral R3c phase at low-content doping. The pressure-induced phase-transition sequences of La-doped BiFeO3, which mixed nanoscale orthorhombic symmetry in the R3c crystal structure were investigated using synchrotron radiation X-ray diffraction up to 27.3 GPa. Our experimental data clearly showed that rohombohedral (R3c) phase first transforms to monoclinic (C2/m) phase at 6.5 GPa, then to orthorhombic (Pnma) phase at 13.5 GPa, and the coexistence of multiple intermediate phases are observed before two transitions, revealing that the doping-induced nanoparticles with orthorhombic structure did drive the change in symmetry and transition pressure.