Mesoscale mechanisms of the diffuse dielectric behaviour and retention of the polar nano-regions in the polycrystalline ferroelectric BaTiO₃

Barium titanate is a classical ferroelectric material that exhibits a jump-like behavior in the order parameter, spontaneous polarization, near the temperature of its transition to the paraelectric phase. This serves as a textbook example of a first-order phase transition, marked by the coexistence of polar and non-polar phase regions. Despite compelling evidence of the gradual phase transformation across Curie temperature (T_C) and partial retention of ferroelectric properties above T_C, the microscopic mechanisms of the phase retention remain unclear. Current study explains temperature anomalies in the macroscopic characteristics of polycrystalline barium titanate by employing complementary macroscopic and local techniques. Our findings reveal that retention of the polar phase regions is driven by the charged defects, which act as the origin of the spatially non-uniform internal electric fields. The insights from this research offer a deeper understanding of the fundamental mechanisms governing ferroelectric behavior and open new possibilities for tailoring materials with phase coexistence for a wide range of technological applications.