High remanent polarization and temperature-insensitive ferroelectric remanent polarization in BiFeO3-based lead-free perovskite
BiFeO3 is the only known single-phase multiferroic material above room temperature, and it has excellent properties. Therefore, BiFeO3-based materials have been extensively investigated. However, its applications have been hindered by temperature sensitivity. Herein, we report a temperature-stable ferroelectric material, 0.675BiFeO3–0.3BaTiO3–0.025LaFeO3–x mol% MnO2 (x = 0–4.0), prepared by a solid-state reaction. The temperature stability of remanent polarization was regulated by changing the doping amount of MnO2 and sintering temperature. The temperature stability has been greatly improved by a slight increase of MnO2 content and sintering temperature. Samples with larger grain size showed not only improved ferroelectric properties, but also excellent temperature stability. Moreover, these samples with excellent temperature stability have small leakage current variation at high temperature and high electric field, which demonstrates the enhanced temperature stability from a new perspective. The sample with a composition of x = 1.0 sintered at 1050 °C has outstanding temperature stability, with remanent polarization variation less than 7% of its room temperature value in the temperature range of 25–155 °C. The effects of MnO2 doping on strain, ferroelectric and leakage current properties were also studied. All samples with MnO2 doping had lower strain, remanent polarization and leakage current density than those of the undoped ones.