Structural Evolution and Multiferroics in Sr‐Doped Bi7Fe1.5Co1.5Ti3O21 Ceramics

Abstract

The ceramics with the composition of SrxBi7−xFe1.5Co1.5Ti3O21−δ (0 ≤ x ≤ 1, SBFCT) were prepared by a citrate–nitrate combustion method, and the phase evolution with an increasing Sr content was investigated. Pure Aurivillius phase SBFCT with a layer number of n = 6 was obtained when x ≤ 0.25, and then the structure collapsed to 5 layers for x = 0.50, then alternating 4 and 5 layers for x = 0.75, and finally 4 layers for x = 1.00. Meanwhile, secondary phase Sr1−mBimFe1−iCoiO3−γ appeared when x > 0.25, which is antiferromagnetic (AFM) and with low resistivity. Enhanced ferromagnetic and ferroelectric properties were observed from single phase SBFCTs at the room temperature, and the ferromagnetic transition temperature (Tc) increases with the Sr doping level x in the single phase range. The remnant magnetization (2Mr) is 2.27 emu/g and the remnant polarization (2Pr) is 2.89 μC/cm2 at an applied electric field of 100 kV/cm for the x = 0.25 sample.