Entropy-Regulated Local Multiphase Polarization States for Near-Zero Energy Loss in Relaxor Ferroelectrics

How to further regulate the size and stability of polar nanoregions (PNRs) remains a fundamental constraint to simultaneously achieving ultrahigh efficiency (η) and large recoverable energy density (W_rec), thereby limiting the development of near-zero-loss dielectric capacitors. Here, guided by phase-field simulations, we propose an entropy-driven local multiphase polarization state in which rhombohedral (R)- and tetragonal (T)-symmetry PNRs of ∼1 nm in size are embedded within a cubic (C) matrix, effectively reducing hysteretic loss by lowering the domain-switching barriers in Bi_0.5Na_0.5TiO₃-based ceramics. Consequently, an ultrahigh η of 95.1%, a large W_rec of 6.8 J cm^-3, and, simultaneously, an ultrafast discharge time of 240 ns are achieved in the high-entropy (1.76R) ceramic capacitors. The results indicate that entropy regulation can facilitate low-loss dielectric behavior, offering a viable approach for designing near-zero-dissipation energy-storage materials.