Electrocaloric Effect: Theory, Measurements, and Applications

The electrocaloric effect (ECE) is a physical phenomenon found in materials with dipolar constituents, that is, with certain dielectric properties. It is manifested in the heating or cooling of an electrocaloric material due to the applied electric field under adiabatic conditions. Electrocaloric effect has been known for many decades; however, the relatively small ECE observed below 2.5 K made it unsuitable for practical applications. Recently, however, materials with large ECE have been predicted and discovered, thus opening the possibility of realizing dielectric refrigeration that has several potential advantages in comparison with other cooling technologies. This chapter provides an extensive introduction to the field, including the basic theory of the electrocaloric phenomenon in ferroelectric, relaxor ferroelectric, and antiferroelectric materials. In addition, a review of various ECE experimental techniques, including indirect and direct experimental techniques, is given together with examples of recent findings obtained in polymeric, perovskite ceramic relaxor, and ferroelectric materials. An overview of various possibilities of the application of the ECE, the comparison with thermoelectric and magnetoelectric materials, and the state of the art of the cooling/heating devices is also presented.