The evolution of structure, properties and polar domains in rare earth and PbTiO₃ co-substituted BiFeO₃ ferroelectric ceramics

BiFeO₃ (BFO) based ferroelectric solid solutions attract long-lasting research interests due to their multi-functionalities including electric/multiferroic/energy-storage properties. However, achievement of large ferroelectric polarization is still highly challenging in BFO based bulk ceramics due to large leakage. In this work, the structure and electrical properties of rare earth Nd- and PbTiO₃ co-modified BFO ceramics have been explored. Based on high temperature in-situ X-ray diffraction and dielectric measurements, a preliminary ferroelectric phase diagram is established, depicting the morphotropic phase boundaries (MPB) and a critical temperature that cannot be correlated to any macroscopic phase transition. The effects of rare earth substitution on structure evolution have been investigated by comparing the results in this work and literature. The accomplishment of ferroelectric switching with giant ferroelectric polarization above 65 μC/cm² is successfully achieved without resorting to quenching treatment. The MPB compositions demonstrate the maximum piezoelectric coefficients and the lowest coercive field, suggesting the “softening” effects. The domain evolutions suggest two coexisting phases in MPB composition distribute separately in different grains.