Ultrahigh Energy Storage in (Ag,Sm)(Nb,Ta)O₃ Ceramics with a Stable Antiferroelectric Phase, Low Domain-Switching Barriers, and a High Breakdown Strength

AgNbO 3 (AN) antiferroelectrics (AFEs) are regarded as a promising candidate for high-property dielectric capacitors on account of their high maximum polarization, double polarization–electric field ( P – E ) loop characteristics, and environmental friendliness. However, high remnant polarization ( P r ) and large polarization hysteresis loss from room-temperature ferrielectric behavior of AN and low breakdown strength ( E b ) cause small recoverable energy density ( W rec ) and efficiency (η). To solve these issues, herein, we have designed Sm 3+ and Ta 5+ co-doped AgNbO 3 . The addition of Sm 3+ and Ta 5+ reduces the tolerance factor, polarizability of B-site cations, and domain-switching barriers, enhancing AFE phase stability and decreasing hysteresis loss. Meanwhile, adding Sm 3+ and Ta 5+ leads to decreased grain sizes, increased band gap, and reduced leakage current, all contributing to increased E b . As a benefit from the above synergistic effects, a high W rec of 7.24 J/cm 3, η of 72.55%, power density of 173.73 MW/cm 3, and quick discharge rate of 18.4 ns, surpassing those of many lead-free ceramics, are obtained in the (Ag 0.91 Sm 0.03 )(Nb 0.85 Ta 0.15 )O 3 ceramic. Finite element simulations for the breakdown path and transmission electron microscopy measurements of domains verify the rationality of the design strategy.