Spatial buffer-area assisted antiferroelectric-ferroelectric transition in NaNbO3

Lead-free antiferroelectric materials can be used in environmental-friendly energy applications and are receiving tremendous attention owing to their high energy-storage density, which is achieved through a phase transition between antiferroelectric and ferroelectric state. Here, by slowing down the antiferroelectric-ferroelectric tran-sition via controllable beam irradiation in a transmission electron microscope, we demonstrate that such a transition in NaNbO3 undergoes by means of forming a buffer-area (about 40-150 nm wide) at the on-going transition front. The spatial buffer-area approximately maintains its shape during moving and are character-ized to be the antiferroelectric phase but exhibits a gradual variation of lattice spacing along the [010] pro-ceeding direction of phase transition. With help of such buffer-area, the overall stress or barrier between the two phases could be considerably reduced compared to the direct change between the two structures. Therefore, our findings provide new insights for understanding the dynamical energy-storage process in antiferroelectric materials.