Rhombohedral–Tetragonal Phase Boundary with High Curie Temperature in (1-x)BiCoO₃–xBiFeO₃ Solid Solution

The crystal structure change of the solid solution BiCo 1- x Fe x O 3 was investigated in order to determine the phase boundary between tetragonal BiCoO 3 and rhombohedral BiFeO 3 . It was found that BiCo 1- x Fe x O 3 with x = 0 to 0.6 had tetragonal BiCoO 3 structures, while those with x = 0.8 to 1 had rhombohedral BiFeO 3 structures at room temperature. The monoclinic √2 a × √2 a × a phase was found for the x = 0.7 sample. The tetragonal-to-cubic phase transition was first observed at around 700–850 °C in Bi-based perovskite for the x = 0.8 sample.