Pressure induced phase transition of La-substituted BiFeO3

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 phasetransition 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.

Automated summary

The structure of La doped BiFeO3 at low doping content is not completely the believed hexagonal R3c phase, but contains an orthorhombic crystal symmetry. Under certain pressure conditions, a phase transition sequence from hexagonal R3c phase to monoclinic C2/m phase and then to orthorhombic Pnma phase was observed in La-doped BiFeO3.