Destruction of conducting channels driven resistivity enhancement in bismuth ferrite-barium titanate based ceramics

Abstract

Bismuth ferrite-barium titanate (BF-BT) based ceramics have attracted extensive attention due to their high Curie temperature. However, the high conductivity and large leakage current greatly limit their high-temperature applications. Although manganese (Mn) was widely utilized in BF-BT ceramics to improve the resistivity, the increase extent is still limited. Inspired by the recently reported ferroelectric/relaxor composite piezoceramics with enhanced strain response, we are considering that composition inhomogeneous may also have an influence on resistivity. In this work, “two-step” method is used to prepare pseudo-composite ceramics in (1-x)[0.7BiFeO3-0.3BaTiO3]/x[(0.7BiFeO3-0.3BaTiO3):1.5 %Mn]. The combination of 0.7BF-0.3BT and (0.7BF-0.3BT):1.5 %Mn is not strictly a composite ceramic, but rather exhibits heterogeneous diffusion of Mn during high-temperature sintering, making it a solid solution with inhomogeneous composition distribution. The maximum resistivity (5.86×106 Ω•cm, at 300 ℃) can be achieved when x = 0.3, which is greatly improved compared to the conventionally processed (one-step method) samples containing the same average amount of MnO2 additive. The enhanced resistivity can be attributed to the inhomogeneous defect distribution induced by the heterogeneous diffusion of Mn, leading to the difficulty of defect carriers to form a conductive channel.