Field-Induced Polarization Rotation in Order-Disorder (K,Na)NbO₃-Based Ferroelectrics

Phase boundary is highly recognized for its capability in engineering various physical properties of ferroelectrics. Here, field-induced polarization rotation is reported in a high-performance (K, Na)NbO₃-based ferroelectric system at the rhombohedral-tetragonal phase boundary. First, the lattice structure is examined from both macroscopic and local scales, implementing Rietveld refinement and pair distribution function analysis, respectively. The macroscopic phase coexistence at the phase boundary can be interchangeably rationalized with an average projection of collective local disordered units, exhibiting the order-disorder nature. The structural evidence of field-induced polarization rotation is provided by the in situ synchrotron study. Theoretical studies including density functional theory calculation and molecular dynamics simulation also predict the polarization rotation mechanism. The simulation result reveals the variation of the degree of ordering during the polarization rotation as a key feature of the boosted electrical properties in the order-disorder ferroelectric system. The discovery provides meaningful insight into the design of ferroelectrics with enhanced physical properties.