A comprehensive review of the electrocaloric effect in lead free ferroelectrics for solid state cooling

Electrocaloric (EC) solid-state cooling technology is attracting interest as a versatile solution for energy-efficient thermal regulation in industrial and electronic applications. Ferroelectric materials, characterized by significant polarization and entropy variations in response to electric fields, offer small, environmentally sustainable cooling systems suitable for integration into sophisticated devices. Recent studies highlight the necessity of lead-free electrochemical materials to comply with ecological and regulatory standards. The article offers a thorough examination of the thermodynamic concepts that regulate EC refrigeration and emphasizes advancements in Pb-free materials, encompassing bulk ceramics, single crystals, thin and thick films, multilayer structures, and polymers. Emphasis is placed on compositional engineering and structural design methodologies that improve electrochemical performance while guaranteeing mechanical dependability for industrial applications. The discussion encompasses modeling and simulation endeavors concerning BaTiO₃ (BT), BaSrTiO₃ (BST), and P(VDF-TrFE) copolymers, as well as novel methodologies for scalable device integration. Ultimately, prospective avenues are delineated for the advancement of multifunctional electrochemical materials and composites that integrate temperature management with structural and energy capabilities for next-generation industrial and electronic systems. Graphical Abstract