Temperature-stable energy storage and fast discharge properties of lead-free bismuth sodium titanate–based dielectric ceramics

Lead-free (1–x)[0.935(Bi₀.₅Na₀.₅TiO₃)–0.065Ba(Ti₀.₉₉Nb₀.₀₁)O₃]+x(NaTaO₃) (BNT–BTNb–NT) ceramics were studied for energy-storage application. The NT incorporation induces a phase transition from a rhombohedral–tetragonal coexistence to a pseudo-cubic structure, enabling improved relaxor characteristics. The composition delivers a high recoverable energy density (Wᵣₑc ≈ 6.40 J·cm⁻³), high sensitivity factor (213 J/kV.m2), power density (350.8 MW·cm⁻³), and ultra-fast discharge speed (t₀.₉ ≈ 43 ns). Moreover, Wᵣₑc and efficiency vary by only 3.2% and 4.9% across 1–100 Hz and by 2.1% and 5.8% over 25–160 °C. Additionally, increasing NT content suppresses dielectric permittivity while significantly broadening the temperature-stable dielectric range. The x = 0.12 composition exhibits widest temperature window of 438 °C from room temperature to 460 °C for temperature coefficient of capacitance ≤ ±15% and stable low dielectric loss (tan δ ≤ 0.05) up to 500 °C. These results suggest the prepared materials are promising for high-temperature capacitors and pulsed power energy storage application.