Stable relaxor ferroelectric phase of NaNbO3-based ceramic with superb energy storage performances

NaNbO3-based ceramics (NN) as a lead-free antiferroelectric (AFE) material has received widespread attention in electrostatic capacitors. Nevertheless, complex structural phase transformation with low threshold switching electric fields hinders the enhancement of energy storage capability. Herein, a feasible avenue for attaining a stable relaxor ferroelectric (FE) phase in NN-based ceramic is designed by introducing Ca0.7Sm0.2TiO3 (CST) to improve the capacitive performance. The experimental results demonstrate that (1-x)NN-xCST ceramics transform from the AFE P to the FE Q phase and domain size evolves from sub-micro to nano-scale as the CST content increases. Meanwhile, the filling behavior of non-isovalent ions induces local random fields caused by the disruption of the long-range polar structure. Ultimately, an ultra-high Wrec ∼9.10 J/cm3 and a desirable η ∼80.1% are attained simultaneously in 0.85NN-0.15CST relaxor FE ceramic, surpassing most NN-based and other lead-free ceramics. Moreover, Wrec and η exhibit excellent stability under the test conditions of frequency, temperature, and cycling. This work demonstrates that the stabilized FE Q phase is an effective approach to accelerate the development of NN-based dielectric materials in advanced energy-storage devices.