High comprehensive energy storage properties in (Sm, Ti) co-doped sodium niobate ceramics

Ceramic capacitors are ubiquitously used in high power and pulse power applications, but their low energy density, especially at high temperatures (>150 °C), limits their fields of application. One of the reasons is the low energy efficiency under high electric fields and/or at high temperatures. In this work, equimolar Sm³⁺ and Ti⁴⁺ cations were doped in NaNbO₃ to increase relaxor characteristics and energy storage properties. The optimal recoverable energy density W_rec of 6.5 J/cm³ and energy efficiency η of 96% were attained in the ceramics with 10% (Sm, Ti) concentration (SmT10). Dense microstructure and low dielectric loss were attributed to the high energy storage performance. Impedance spectra analysis revealed that the grain boundary resistance dominates at low temperatures, while the grain resistance dominates at high temperatures. The ceramics show stable W_rec and η in a broad temperature range of −90 to 200 °C and repeated charge-discharge cycles up to 10⁵. The comprehensive energy storage performance indicates SmT10 ceramics are among potential candidates for ceramic capacitors working at high temperatures.