Highly Tunable Multifunctional BaTiO3-Based Ferroelectrics via Site Selective Doping Strategy

Electric-field-driven polarization in ferroelectrics delivers extraordinary electro-caloric, electro-optic, and electromechanical properties, etc. However, the controllable multifunctional ferroelectric switching between different electro-related performances still faces great challenges and deserves study. Herein, multifunctional BaTiO ₃ (BT)-based ferroelectrics are conceived tuning electrocaloric and electrostrictive properties by controlling doping site of dopants, namely site selective doping strategy. The well-concerned Ce is selected for its multivalent trait (Ce ³⁺/Ce ⁴⁺ ) and effective adjustment of Curie temperature ( T _C ) in BT. Guided by the distinguished dielectric characteristics via doping Ce ³⁺ in Ba site or Ce ⁴⁺ in Ti site, BT-based ferroelectrics can direct at different applications. For Ba-site doping, in conjunction with ion-size mismatch effect and defect engineering, manipulating T _C to room temperature (RT) and driving second-order-like phase transition are obtained simultaneously. Then, large electrocaloric temperature change (∆ T_max=1.3 K) over a broad temperature span (∆ T>1 K, 37~70 ℃) is achieved, which is crucial in developing zero-global-warming-potential refrigeration near RT. For Ti-site doping, unique diffuse phase transition is observed without sacrificing T _C , leading to multiphase structures and the formation of nanosize domains, hence facilitating polarization rotation. Therefore, an enhanced electrostrictive strain ( S>0.17%) with ultra-low hysteresis ( H_hyst<5%) among a wide temperature range is obtained, which challenges toxic lead-contained counterparts in actuators.