Structural, optical, and magnetic properties of compositionally complex bismuth ferrite (BiFeO3)

Abstract

Compositionally complex ceramics (CCCs) is an extended version of high entropy ceramics (HECs) concept where compositional space has been broadened by the inclusion of non-equimolecular compositions and relatively low entropy options to provide more flexibility in tuning the properties of materials. This study is the first experimental demonstration of the novel CCCs concept in multifunctional bismuth ferrite (BiFeO3). Compositionally complex bismuth ferrite (CCBFO) samples were prepared by conventional solid-state reaction method through the incorporation of five different cations in Fe sites, BiFe1–5xMoxTixZrxNixCexO3 (x = 0.01, 0.02, 0.03). Reitveld refinement reveals notable distortion in the rhombohedral R3c-type structure with a significant change in Fe–O–Fe bond angle from its ideal value of 180° to 100.2°. Mesoporous-type morphology with a substantial amount of interconnected porosity is observed from SEM micrographs. To prove the utility of the samples, optical and magnetic properties have been investigated. Bandgap value reduces to 2.12 eV from 2.86 eV with the increment of doping from 5 to 15%. M–H curve from VSM analysis indicates weak ferromagnetic behavior with narrow coercivity in all samples instead of ideal antiferromagnetism in BiFeO3. The highest saturation magnetization of 0.45 emu/gm is seen in 15%-doped CCBFO. These changes in properties are also in good agreement with the measured structural and morphological parameters. The obtained results suggest that CCCs concept can be effectively used to tune the properties of multifunctional ceramic oxides and careful selection of cations might improve the functionalities even to a new extent.