Influence of La doping on multiferroic properties of BiFeO3 ceramics prepared by the melt-quenching method

In recent decades, much attention has been attracted to the multiferroic materials which were expected to give rise to novel properties and multifunctional applications. In this communication, lead-free multiferroic Bi1-xLaxFeO3 ceramics with x = 0, 0.025, 0.05, 0.1, 0.15, and 0.2 were prepared by the melt-quenching method. The influence of La doping on microstructure, dielectric, ferroelectric properties, and leakage current characteristics was investigated. XRD results showed that the generation of secondary phases (mainly Bi25FeO39) was decreased gradually when doping content was below 0.1, but it increased rapidly with La content increasing to 0.2. In addition to this, it could be found that the split reflections of (104) and (110) shifted to a higher value, which proved La doping would cause a structural distortion. SEM images indicated that the melt-quenching method would lead to a columnar crystal which disappeared gradually with the increase in La content. The dielectric constant firstly increased from 178 of x = 0 to 256 of x = 0.1 and then decreased to 165 of x = 0.2 at 10 kHz, while the dielectric loss increased from 0.11 of x = 0 to 0.28 of x = 0.2 with La doping. The value of remnant polarization was significantly improved from 0.05 of x = 0 to 1.19 μC/cm2 of x = 0.2, but TC decreased from 450 to 376 °C. Besides, the leakage current density values of all La-doped samples were about one order of magnitude higher than that of pure BiFeO3. These changes were closely related to the content of secondary phases, change of grain size, and increase in carriers.