Phase transition and enhanced electrical properties in 0.725BiFeO3-0.275Ba0.85Ca0.15Ti0.9Zr0.1−xSnxO3 multiferroic ceramics

•A pseudocubic–rhombohedral and relaxor–normal ferroelectric transition observed.•The grain growth and densification are obviously facilitated by Sn doping.•The piezo-, ferro- and dielectric properties are enhanced, and TC increases linearly.

Lead-free 0.725BiFeO3-0.275Ba0.85Ca0.15Ti0.9Zr0.1−xSnxO3 (BF-BCTZS-1000x, x = 0, 0.025, 0.050, 0.075, 0.100) multiferroic ceramics were fabricated via a conventional solid-state reaction method. Effects of Sn substitution on the structural, electrical and magnetic properties have been studied. The XRD patterns reveal that the pseudocubic structure of the ceramics transforms into rhombohedral after Sn substitution for Zr. The SEM images show that Sn doping effectively facilitates the grain growth and densification of the ceramics. Room-temperature dielectric properties are apparently improved. The temperature-dependent dielectric results show that the Curie temperature of the BF-BCTZS-1000x increases almost linearly from 401.0 °C to 418.8 °C with the increasing Sn content, and the diffusivity γ of the system decreases from 1.958 to 1.361. Both remnant polarization and hysteresis loop squareness of BF-BCTZS-1000x ceramics are improved obviously after Sn substitution. Piezoelectric coefficient shows a sharp increase after Sn substitution and decreases slightly with further increase of Sn content. Weak ferromagnetism is revealed in all BF-BCTZS-1000x ceramics, but is weakened for Sn-doped samples.