Dielectric and energy storage performances of Na0.7Bi0.1NbO3 relaxor ferroelectric ceramics with submicron grain size fabricated via cold sintering

•Na0.7Bi0.1NbO3 ceramics were fabricated at low temperatures (750–900 °C) by cold sintering assisted with heat treatment.•Relatively dense microstructure and submicron grain size (0.41–0.73 μm) were achieved.•NBN ceramic heat-treated at 850 °C exhibited the excellent energy storage performance (Wrec = 1.78 J/cm3 @ 270 kV/cm). NaNbO3 is a prominent lead-free antiferroelectric ceramic used in energy storage, and Na0.7Bi0.1NbO3 ceramics synthesized by the solid-state method demonstrate superior energy storage performances because of the decreased remnant polarization and increased saturated polarization caused by the incorporation of Bi3+. However, the higher temperature (>1150 °C) of conventional sintering leads to serious volatilization of Na and Bi. In this work, Na0.7Bi0.1NbO3 ceramics were fabricated at significantly lower temperature (750–900 °C) by cold sintering assisted with heat treatment. Na0.7Bi0.1NbO3 ceramics show relatively dense microstructure and submicron grain size (0.41–0.73 μm), and there are obvious relaxor behaviors observed in all samples. Benefiting from the excellent insulating property and submicron grain size, the Na0.7Bi0.1NbO3 ceramic heat-treated at 850 °C has the maximum recoverable energy storage density of 1.78 J/cm3@270 kV/cm among all samples. This work provides a strategy that is more energy-efficient and suitable for the fabrication of NaNbO3-based ceramics with volatile elements. [Display omitted]