Sequential Phase Transitions in Sm Substituted BiFeO3

The compositional and thermal evolution of the crystal structure of the solid solution Bi 1-x Sm x FeO 3 synthesized at a high pressure of 4 GPa was investigated. It was found that Bi 1-x Sm x FeO 3 with $x = 0.10$ and 0.15 had an antipolar PbZrO 3 -type structure with a $\sqrt{2}a\times 2\sqrt{2}a\times 4a$ perovskite superstructure at room temperature, while that with $x = 0.05$ had the same structure as the parent BiFeO 3 ($x = 0$). The $x = 0.10$ sample transforms from an antipolar PbZrO 3 -type orthorhombic structure to a polar BiFeO 3 -type rhombohedral structure and eventually to a nonpolar GdFeO 3 -type structure on heating as Zr-rich PZT.