Synergistic multi-ion doping in BaTiO₃-based ceramics: Achieving high electrocaloric efficiency and wide temperature span for miniaturized cooling application

Electrocaloric cooling, a solid-state refrigeration technology utilizing the electrocaloric effect (ECE), enables miniaturized cooling systems. However, its practical application is constrained by limited adiabatic temperature change (Δ T ), restricted operating temperature span ( T span ), and the fact that peak performance typically occurs at elevated temperatures. To overcome this, (1-x)Ba₀.₇₆Sr₀.₂₄TiO₃-xCa(Ti₀.₉Sn₀.₁)O₃ (BST-CS) lead-free ferroelectric ceramics were synthesized via solid-state reaction, enhancing Δ T and T span through multi-ion doping. XRD and Raman spectroscopy confirmed tetragonal (T) and pseudo-cubic (PC) phase coexistence, with the PC phase increasing with doping. Temperature-dependent Raman and dielectric spectra revealed a tetragonal-cubic transition near the Curie temperature, contributing to the ECE. The optimized composition ( x  = 0.14) achieved Δ T  = 1.74 K and T span = 52 K (40–90°C, Δ T  ≥ 80 % of Δ T max ) under 50 kV·cm −1 . Phase coexistence lowers polarization barriers, while grain refinement improves breakdown strength. This work advances eco-friendly microelectronics cooling by balancing performance and practicality.