Fe doping effect on the structural, ferroelectric and magnetic properties of polycrystalline BaTi_1−xFe _xO₃ ceramics

BaTi_1−xFe_xO₃ (x = 0–0.08) ceramics were prepared by conventional solid-state reaction. The Fe doping effect on the structure, electrical and magnetic properties was analyzed. The Fe substitution would reduce the degree of tetragonality and ferroelectricity. The hexagonal phase began to emerge and increased after x = 0.04 by the X-ray diffraction. Meanwhile, ferroelectricity is diminished due to an increase of the non-ferroelectric hexagonal and pinning of domain wall motioned by oxygen vacancies with the increasing Fe substitution. It is found that the nonlinear change of magnetic properties with the increasing Fe concentration. The critical role of the valence state of Fe ions and the accompanied oxygen vacancies on the magnitude of magnetic properties is discussed. Our investigations suggest that the competition of Fe⁴⁺–O²⁻–Fe⁴⁺, Fe³⁺–O²⁻–Fe⁴⁺ and Fe³⁺–O²⁻–Fe³⁺ interaction are coexisted, and the Fe⁴⁺–O²⁻–Fe⁴⁺ super-exchange interaction is responsible for the larger magnetism at x = 0.04. From the analyze of XPS spectra, the higher content of Fe⁴⁺ and lower oxygen vacancies at x = 0.04 verify that Fe⁴⁺–O²⁻–Fe⁴⁺ super-exchange interaction is the origin of larger magnetism.