Advanced materials for solid-state refrigeration

Abstract

Recent progress on caloric effects are reviewed. The application of external stimuli such as magnetic field, hydrostatic pressure, uniaxial stress and electric field give rise respectively to magnetocaloric, barocaloric, elastocaloric and electrocaloric effects. The values of the relevant quantities such as isothermal entropy and adiabatic temperature-changes are compiled for selected materials. Large values for these quantities are found when the material is in the vicinity of a phase transition. Quite often there is coupling between different degrees of freedom, and the material can exhibit cross-response to different external fields. In this case, the material can exhibit either conventional or inverse caloric effects when a field is applied. The values reported for the many caloric effects at moderate fields are large enough to envisage future application of these materials in efficient and environmental friendly refrigeration.

Influence of epitaxial strain on elastocaloric effect in ferroelectric thin films

“…Immediately, one can see that the TECs are negligible in the paraelectric phase according to Eqs. (4) and (5). This behavior is also confirmed by a recent thermodynamic model showing that both the conventional elastocaloric response 29 and inverse barocaloric effect 30 in BTO single crystals disappear in the paraelectric phase.…”

“…4 On one hand, ferroelastic shape memory alloys are most intensively studied and promising elastocaloric materials due to their excellent superelasticity and broad operational temperature window. [5][6][7][8][9] On the other hand, ferroelastic ferroelectric bulk and thin films are predicted to have remarkable elastocaloric properties comparable with ferroelastic martensites, [10][11][12] which further expands the elastocaloric family.…”

“…Note that 6.9 K is indeed in the range of temperature changes for other elastocaloric systems reported in the literature. [2][3][4][5][6][7][8][9][10][11] Moreover, due to the second-order nature of the phase transition, it is expected that the hysteresis loss and irreversibilities associated with latent heat vanish, which is of importance to enhance refrigerant efficiency. 5,12,13 In addition, the system can operate in a wide temperature window for all compressive substrates we investigated (see, e.g., the 60 K FIG.…”

“…(4) contributes to the elastocaloric effect due to its temperature dependence (since it is straightforward to prove that P 0 depends on a 1 ). The elastocaloric change in temperature DT r 3 upon application of a stress field in adiabatic conditions can be determined by 5,12 …”

Combined caloric effects in a multiferroic Ni–Mn–Ga alloy with broad refrigeration temperature region

“…Consequently, it is regarded as the most promising candidate to replace traditional vapor-compressing refrigeration technology. [1][2][3][4][5][6][7] By applying external stimulus, such as magnetic, electric, or stress fields on these ferroic materials, the corresponding caloric effects, such as magnetocaloric (MC), electrocaloric (EC), and elastocaloric (eC) effects, would be obtained, for ferromagnets, ferroelectrics, and ferroelastics, respectively. 1,5,6 However, the refrigeration temperature regions of most caloric effects are usually in a limited scale due to the narrow phase transition region of ferroic materials, which has been a key drawback for applications.…”