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 1/2 Nb 1/2 )O 3 - x Pb(Mg 1/3 Nb 2/3 )O 3 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 (Δ T ) of 3.48 K, a robust ECE strength (Δ T /Δ E ) 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 Q 33 of 0.007 m 4 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 Δ T and low electrostrains, presenting promising advancements in ECE applications with an extended lifetime.