Novel pyrochlore-type Sm2Ti2O7 ceramics with ultrahigh energy efficiency and superior energy-storage density

A high energy-storage capacity, coupled with high energy efficiency and breakdown strength, is vital for advancing pulsed-power dielectric capacitors. This study introduces a novel linear dielectric ceramic, Sm2Ti2O7, characterized by a pyrochlore structure. The Sm2Ti2O7 ceramic exhibits a highly symmetrical phase structure characterized by a uniform and stable charge distribution. This structural feature enables rapid responsiveness to external electric fields and is accompanied by low dielectric loss, thereby attaining an exceptionally high level of intrinsic energy storage efficiency (about 93.5 %). The material exhibits a substantial band gap of approximately 3.63 eV, as validated through a synthesis of first-principle calculations and experimental data. Simultaneously, uniform and dense microstructures in the ceramic minimize internal defects, which helps prevent heat accumulation during charge/discharge processes, contributing to the high dielectric breakdown strength (approximately 1500 kV/cm). Additionally, it achieves an impressive recoverable energy storage density of around 6.36 J/cm3. The samples exhibit good temperature independence (ΔWrec < ±5% and Δη < ±4.4 % at 25–140 °C), frequency stability (ΔWrec < ±5% and Δη < ±0.9 % at 10–220 Hz), and ultrafast instantaneous discharge time (∼1.12 μs). The pyrochlore-type Sm2Ti2O7 ceramic, with its low heat accumulation and high energy storage density, shows significant potential for the development of advanced pulsed dielectric capacitors.