High‐temperature powder neutron diffraction experiments are conducted around the reported β–γ phase transition (∼930 °C) in BiFeO 3 . The results demonstrate that while a small volume contraction is observed at the transition temperature, consistent with an insulator–metal transition, both the β‐ and γ‐phase of BiFeO 3 exhibit orthorhombic symmetry; i.e., no further increase of symmetry occurs during this transition. The γ‐orthorhombic phase is observed to persist up to a temperature of approximately 950 °C before complete decomposition into Bi 2 Fe 4 O 9 (and liquid Bi 2 O 3 ), which subsequently begins to decompose at approximately 960 °C.
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Arnold et al. (2010) studied this question.