Ferroelectrics in Electrocaloric Cooling

Electrocaloric effect (ECE) in polarizable dielectric materials has great potential for application in solid-state cooling devices with compact size and high efficiency. This chapter elaborates systematically the fundamentals of electrocaloric effects with the aid of the classical thermodynamics theory, Landau–Devonshire phenomenological theory, and the statistical thermodynamics theory. Positive ECE and negative ECE are classified. The device design of electrocaloric refrigerator prototype is described based on the basic thermodynamic cycles. The ECE in ferroelectric bulk ceramics, thin films, ferroelectric polymers, and other materials (the composites, liquid crystals and fast ion conductors) is reviewed and summarized. A basic conclusion is that for practical cooling devices, the electrocaloric material must possess a large isothermal entropy change and a large adiabatic temperature change simultaneously in a broad range of temperatures near room temperature.