Effect of nonstoichiometry on the structure and dielectric properties of bismuth ferrite

Reasons for the High Electrical Conductivity of Bismuth Ferrite and Ways to Minimize It

“…BiFeO 3 begins to form in the temperature range of 770 ≤ T 1 ≤ 820 K; Bi 25 FeO 39 (sillenite phase) appears earlier at lower temperatures of~720 K and is an intermediate compound; Bi 2 Fe 4 O 9 (mullite phase) is present in BiFeO 3 at the stage of improving its structure (920 ÷ 1020 K) as a concomitant compound. Its formation is the result of structural A-non-stoichiometry of BiFeO 3 [39], a phenomenon typical of oxygen-octahedral compounds with the ReO 3 structure [40] and perovskite [41][42][43] containing ions of variable valence. A specific feature of such substances is the ability of a crystallographic shift to exclude an appearance of anionic vacancies (for various reasons), and in complex oxides (of the perovskite type), their equal number of cuboctahedral positions.…”