Enhancing electrocaloric effects of KNN-based ceramics by phase- and ion-configurational entropy regulation based on phase-field modeling

Potassium-sodium niobate (KNN)-based piezoelectric materials demonstrate exceptional electrocaloric (EC) optimization potential owing to phase configurational diversity, though current performance remains constrained by insufficient entropy modulation. This study establishes high-entropy strategies—particularly phase/ion-configurational entropy (I-PCE) synergistic regulation—as a critical pathway to transcend conventional EC entropy change (ΔS_ECE) limits. Phase-field modeling of Rhombohedral-Orthorhombic-Tetragonal-Cubic (R-O-T-C) phase evolution reveals that ΔS_ECE is governed by three hierarchical factors: phase configurational entropy (S_{config_phase}, dominant), ion configurational entropy (S_{config_ion}), and polarization response. Notably, polarization response in R-phase supersedes O-phase entropy contributions, establishing a performance hierarchy. Based on I-PCE optimization, R-O-dominated multiphase coexistence achieves a ΔS_ECE exceeding 19 J/kg/K at 52.80 μC/cm² reversible polarization. Further achieving enhanced polarization (100 μC/cm²) yields a ΔS_ECE of 73 J/kg/K, establishing the experimental EC upper bound for KNN systems via high entropy-driven design. We anticipate that these discoveries will provide theoretical guidelines for tailoring EC effects in multiphase-configurational material systems via high-entropy strategies.