Synergistic effect of Orthorhombic–Cubic phase coexistence on breakdown strength in (1−x)NaNbO ₃ – <i>x</i> CaZrO ₃ ceramics

Dielectric ceramics with high charge–discharge rates and power density are promising for advanced power electronic applications. In this work, high-performance ([Formula: see text])NaNbO 3 –xCaZrO 3 (([Formula: see text])NN–xCZ) lead-free ceramics were designed through coordinated regulation of phase structure and microstructure. X-ray diffraction and Rietveld refinement confirmed the coexistence of orthorhombic (P21ma) and cubic (Pm-3m) phases in all samples. Increasing CZ content promoted cubic phase formation and reduced remanent polarization, indicating a transition to a relaxor ferroelectric state. At [Formula: see text], the ceramics exhibited the smallest grain size, highest density and optimal synergy of local stress, interfacial polarization and defect control, achieving a breakdown strength of 620[Formula: see text]kV cm[Formula: see text]. The polarization–electric field (P–E) hysteresis loop was quasi-linear, with a recoverable energy density of 3.891[Formula: see text]J/cm 3 and an energy efficiency of 74.1%. These results demonstrate the critical role of CaZrO 3 doping in enhancing structure–property relationships, providing an effective strategy for developing high-performance, lead-free energy storage ceramics.