Room temperature synthesis of Bi25FeO39 and hydrothermal kinetic relations between sillenite- and distorted perovskite-type bismuth ferrites

Abstract

The time-dependent study at mild hydrothermal conditions revealed the kinetic relation between structurally unrelated bismuth ferrites. We report the synthetic conditions that disclose the in situ transformation of Bi₂₅FeO₃₉ into BiFeO₃ by only extending the time for crystallization. We also demonstrate how a careful investigation of the early stages of multiferroics crystallization provides cheap and easy room-temperature access to the important sillenite-type of structure of Bi₂₅FeO₃₉. The crystal structure analysis by the Rietveld method and magnetization measurements provided detailed structure and magnetic relations between the synthesis conditions and the properties of the run product. The BiFeO₃ antiferromagnetic behavior with a small ferromagnetic component arising from the particle's surface uncompensated spins is ascertained.