A novel low-loss and high-stability (1-x)Na0.98NbO3–xBi(Al0.5Y0.5)O3 lead-free composite ceramics for dielectric energy storage capacitors

Environmentally friendly, high-performance, lead-free dielectric ceramic capacitors are urgently required for efficient and clean energy storage devices. However, most ferroelectric capacitors require excessively high electric fields to achieve large energy storage densities. In this study, we designed and fabricated a (1-x)Na0.98NbO3–xBi(Al0.5Y0.5)O3 (abbreviated as (1-x)NN-xBAY) composite system with different BAY doping levels using a traditional solid-state reaction method. By introducing 12 mol% BAY into nonstoichiometric NN, the polarization–electric field loop of the 0.88NN–0.12BAY ceramic became significantly slender and showed a superior relaxor behavior. Consequently, a remarkably low dielectric loss of tanδ < 0.005, high energy storage density of ∼ 4.64 J/cm3, and high efficiency of ∼ 85.98 % were simultaneously obtained in the 0.88NN–0.12BAY ceramic under a moderate electric field of 223.47 kV/cm. Furthermore, it exhibited ultrahigh stability in the temperature range of 25–200 °C and wide frequency range of 1–200 Hz, even after 108 electrical cycles. This study demonstrated a promising candidate material for energy storage devices operating under low or medium electric fields.