Thermal stability of dielectric and energy storage performances of Ca-substituted BNTZ ferroelectric ceramics

In this study, we synthesized [Ca_x(Bi₀.₅Na_0.5)_1−x](Ti₀₈₅Zr_0.15)O₃ (Ca-substituted BNTZ) ferroelectric ceramics with x = 0–0.15 using a solid-state reaction technique. The structural evolution of Ca-substituted BNTZ was revealed by X-ray diffraction combined with Rietveld crystal structure refinement. A pseudocubic structure with P4bm symmetry is suggested for all Ca-substituted BNTZ samples. Temperature-dependent dielectric properties show a clear and broad dielectric peak of approximately 340 °C. The dielectric peak becomes even wider, and the thermal stability of the permittivity is dramatically improved when x gradually increases. In the x = 0.10 composition, the permittivity at 25–450 °C varies between +5% and −14.5%. A recoverable energy storage density (W_rec) of 2.79 J/cm³ with an energy storage efficiency (η) of 76% was achieved in the x = 0.07 composition, which suggests superior properties over other BNT-based systems. In addition, the compositions of x = 0.07, 0.10 and 0.15 show excellent thermal stability of W_rec and η. This work proves that the thermal stability of dielectric and energy storage performances in BNT-based ferroelectric ceramics can be achieved by introducing ions without contributing to the polarization.