Large electrocaloric effect and broad temperature span in BaTiO3 ceramics via phase coexistence strategy

Electrocaloric effect (ECE), a promising candidate for advanced solid-state refrigeration technology, faces fundamental limitations in simultaneously achieving large adiabatic temperature change (Δ T ) and broad working temperature span ( T span ). Here, we strategically designed a component system of Ba 1- x (Li 0.5 Sm 0.5 ) x Ti 1- y Zr y O 3 ( y BZT- x LS) which establishes the coexistence of multiple ferroelectric phases near room temperature. In this system, the heterovalent Li + /Sm 3+ doping at A-site induces relaxor behavior and promotes the coexistence of orthorhombic-tetragonal (O-T) phases around room temperature. Based on this, the addition of Zr 4+ at B-site further increases relaxation degree and constructs a broad temperature window with contiguous polymorphic phase transition, thereby facilitating the coexistence of rhombohedral-orthorhombic-tetragonal (R-O-T) phases. Direct ECE measurements on the optimized 0.02BZT-0.08LS composition reveal a maximum Δ T (Δ T max ) of 2.3 K at 40 °C and a broad T span (Δ T  ≥ 90% Δ T max ) over the practical operating range from 20 to 70 °C.