Electrocaloric Effect: Theory, Measurements, and Applications

Abstract

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.

Electrocaloric effects in the lead-free Ba(Zr,Ti)O3 relaxor ferroelectric from atomistic simulations

“…The electrocaloric (EC) effect characterizes the change in temperature induced by a change in electric field [1][2][3][4][5][6], with the electrocaloric coefficient being defined as α =…”

Electrocaloric and elastocaloric effects in soft materials

“…in materials with inducible dipoles [1]. It requires a coupling of the electric field to dipolar entities which by changing the electric field will result in changes of the dielectric subsystem entropy [2]. The ECE is manifested in the heating or cooling of an EC material due to the application or removal of the electric field under adiabatic conditions, respectively.…”

Direct and indirect measurements on electrocaloric effect: Recent developments and perspectives

“…1 This phenomenon is called the electrocaloric effect, which is considered as a new refrigeration solution to replace current vapor-cycle cooling technologies. [1][2][3][4][5][6][7][8][9][10][11][12] It is now known that electrocaloric materials often exhibit the largest response near their phase transitions. related to ferroelectric/antiferroelectric/relaxor ceramics were reported, but the best electrocaloric effect data yielded an adiabatic temperature change of less than 2.5 K in Pb 0.…”

“…Since then this indirect measurement, based on the Maxwell relations, has become a well-established practice in the field. [1][2][3][4][5][6][7][8][9][10][11][12] This approach is useful for rapid selection of electrocaloric materials. However, uncertainties can arise when improper methods are used in such approach.…”

“…Therefore, this review is intending to bring an overview on the current electrocaloric measurements complementary to other excellent works, i.e., a recent book 1 and other reviews, 2-12 which we strongly recommend to readers. We address recent developments that were not systematically and comprehensively discussed or focused on in the previous works [1][2][3][4][5][6][7][8][9][10][11][12] especially during the past three years, such as selection of polarization-electric field PðEÞ loops, negative electrocaloric effect in antiferroelectrics, controversial debate on the indirect method in relaxors, the important role of field dependence of specific heat, kinetics factors, and so on. Our aim is to gain deeper insights into electrocaloric effect by addressing the indirect method based on Maxwell relations while emphasizing the direct measurements to set a solid foundation for developing electrocaloric prototypes.…”