Study on superstructure in ion co-doped BiFeO₃ by using transmission electron microscopy

La³⁺ and V⁵⁺ co-doped BiFeO₃ ceramics are synthesized by rapid liquid sintering technique. The modulated structure in Bi_0.85La_0.15Fe_0.97V_0.03O₃ is investigated by using transmission electron microscopy (TEM). Two kinds of superstructures are observed in the samples. One is the component modulated superstructure and twin-domain, which is generated by La³⁺ ordered substitution for Bi³⁺ and frequently appears. The chemical composition of the superstructure is explored by x-ray energy dispersive spectroscopy (EDS). The model of the ordered structure is proposed. Simulation based on the model is conducted. The second is the fluorite-type δ-Bi₂O₃ related superstructure. The relation between the ferroelectric property and the microstructure of the sample is also discussed.