Engineering Multiphase Phase Transitions for Exceptional Electrocaloric Performance and Ultraweak Electrostrictive Response in Ferroelectrics

In the pursuit of eco-friendly alternatives for refrigeration technology, electrocaloric materials have emerged as promising candidates for efficient solid-state refrigeration due to their high efficiency and integrability. However, current advancements in electrocaloric effects (ECEs) are often constrained by high temperatures and elevated electric fields (E-field), limiting practical applicability. Informed by phase-field simulation, this study introduces a (1-x)Pb(Yb_1/2Nb_1/2)O₃-xPb(Mg_1/3Nb_2/3)O₃ system, strategically engineered to incorporate highly ordered YN and disordered MN mixtures. The synergistic interplay between E-field/temperature-induced polarization reorientation and cation shift initiates multiple ferroelectric-antiferroelectric-paraelectric phase transitions. Our results demonstrate that under a moderate E-field of 50 kV cm^-1, the x = 0.22 composition achieves remarkable performance with a giant temperature change (ΔT) of 3.48 K, a robust ECE strength (ΔT/ΔE) of 0.095 K cm kV^-1, and a wide temperature span (T_span) of 38 °C. Notably, the disrupted lattice structure contributes to ultralow electrostrains below 0.008%, with an average electrostrictive coefficient Q₃₃ of 0.007 m⁴ C^-2. The significantly weakened electrostrictive activity favors enhancing the performance stability of subsequent devices. This work introduces an innovative strategy for developing robust electrocaloric materials, offering substantial ΔT and low electrostrains, presenting promising advancements in ECE applications with an extended lifetime.