Electric Field‐Induced Phase Transition Behaviour in Sodium Bismuth Titanate‐Based Ceramics

Lead‐free sodium bismuth titanate (Na 0.5 Bi 0.5 TiO 3 , NBT)‐based ceramics have emerged as leading candidates to replace Pb‐based piezoelectric materials due to their promising ferroelectric and piezoelectric performance. Their functional performance remains governed by an appropriate balance between relaxor dynamics, field‐induced ferroelectricity and compositionally driven structural instability. This review presents a framework linking these behaviours to three geometric descriptors: the classical tolerance factor (t), the new tolerance factor (τ) and octahedral tilt strength (μ), which together dictate ergodic or non‐ergodic relaxor behaviour. After reviewing a few popular NBT‐based solid solutions, experimental evidence shows that non‐ergodic relaxors arise only in low‐t, high‐τ, strongly tilted lattices that can stabilise field‐induced ferroelectric order, whereas increasing t weakens tilt coherence, producing ergodic states with dynamic polar nanoregions, resulting in constricted and slim polarisation hysteresis. These insights not only rationalise the challenge of the ferroelectric behaviour reported in current NBT‐based systems but also provide future research opportunities for both non‐ergodic and ergodic relaxors NBT‐based ceramics.