Fig. 1: Structural order differentiation engineering.

Schematic diagram of weak antiferroelectric-ferroelectric first-order phase transition controlled by structural order differentiation engineering, in which the AFD state represents oxygen octahedra distortion mode of antiphase rotation with a tilt angle of about 9.3° along [100] direction12, the weak and the strong AFD states respectively represent distortion modes with smaller and higher tilt angles, and the darkening of FD color blocks indicates a reduced octahedra distortion.