Enhanced piezoelectric performances induced by the flatten Gibbs free energy of BiFeO3-based ceramics

Herein, the 0.725Bi1-xLaxFe0.985Sc0.015O3 − 0.275BaTiO3 (x = 0, 0.005, 0.010, 0.015; abbreviated as 0La, 5La, 10La, 15La, BLFS-BT) with additive of MnO2 were prepared with traditional ceramic technologies. Pure perovskite structures of the BLFS-BT were detected comprising both of the rhombohedral (R) and the tetrahedral (T) phases. The increased La3+ gradually refined the grain sizes, and the Curie temperature of the BLFS-BT decreased from 523 °C to 490 °C that might caused by potential magnetic refrigeration of La. The La3+ not only improved the polarization (Pr), but also weakened the coercive field (Ec) of ceramics, resulting in the enhancement of ferroelectric properties. According to the Landau theory, the Gibbs free energy of the 5La was flatter than other samples, which was conducive to overcoming the energy barrier and forming high polarization, thus producing a better piezoelectric response. A peak d33 value of 160 pC/N was observed in 5La.