High Electrocaloric Effect in Ferroelectrics

Birks, E.; Dunce, M.; Sternberg, A.

doi:10.1080/00150193.2010.505854

Cited by 20 publications

(8 citation statements)

References 27 publications

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“…In the case of ferroelectrics, where dielectric displacement D approximately equals the polarization P, this yields a ΔT EC of [4] ΔT…”

Section: Refrigeration 22mentioning

confidence: 99%

“…The latter is a vector field describing the electrical effect of free and bound charges in materials. Compared to VCR, the E plays the role of pressure and D plays the role of volume in vapour compression.More detailed descriptions can be found in a number of recent reviews of the EC effect [2,4,5] and its application in refrigerators [3,6,7], and a book on this topic [8]. …”

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confidence: 99%

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Electrocaloric Cooling

Suchaneck¹,

Pakhomov²,

Gerlach³

2017

Refrigeration

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The electrocaloric effect describes a reversible temperature change in dielectric materials submitted to an applied electric field. Adiabatic polarization raises their temperature, and adiabatic depolarization lowers it, analogous to temperature changes that occur when a gas is compressed or expanded. For refrigerator application, the reverse Brayton cycle is currently the most promising for practical implementation. The electrocaloric effect provides a large material efficiency. However, existing refrigerator prototypes lack from the absence of efficient heat switches for thermal linkage to the load and the heat sink. Cooling power densities of a few W/cm 2 and temperature spans in the order of 20 K (in regeneration systems) are achievable at a cycle time of 100 ms.Keywords: electrocaloric effect, thermodynamic cycles, coefficient of performance, refrigeration devices IntroductionFor almost 150 years, refrigeration applications were solved by means of vapour compression. While the most efficient fluids for this approach are based on chlorofluorocarbons, hydrochlorofluorocarbons and hydrofluorocarbons, they come with the severe drawback of contributing to global warming and ozone depletion. Therefore, in 1987, the Montreal Protocol issued a ban on these chemicals providing regulations for phasing them out. Promising natural alternative substances are impractical due to their toxicity (ammonia) or-in particular-their flammability (propane) [1].Vapour compression refrigerators (VCRs) are operated as reverse Rankine cycles. They use a circulating liquid refrigerant as a medium. The refrigerant is: (i) adiabatically compressed, (ii) condensed at constant pressure undergoing a phase transition (thereby rejecting heat to the heat sink), (iii) adiabatically throttled in an expansion valve and (iv) evaporated at constant © 2017 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.pressure undergoing the reverse phase transition (thereby absorbing heat from the load). The amount of transferred heat is determined by the latent heat of the first-order phase transition. Similarly, in solid-state electrocaloric (EC) cooling, the adiabatic compression/expansion of the refrigerant is analogous to adiabatic polarization/depolarization, while the isobaric processes are replaced by isofield ones. Contrary to VCR, where the adiabatic expansion of the vapour is thermodynamically irreversible, the EC and the magnetocaloric (MC) effects are thermodynamically reversible processes that could reach the limit of the Carnot efficiency. This is another aspect making them promising for future application.Electric fields required for the EC refrigeration cycle can be supplied much easier and less expensively than the high magnetic fields required for the MC refrigeration [2]. Other advantages in compar...

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“…In the case of ferroelectrics, where dielectric displacement D approximately equals the polarization P, this yields a ΔT EC of [4] ΔT…”

Section: Refrigeration 22mentioning

confidence: 99%

mentioning

confidence: 99%

Electrocaloric Cooling

Suchaneck¹,

Pakhomov²,

Gerlach³

2017

Refrigeration

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“…[9,10] The main EC performance parameters are isothermal entropy change (ΔS) and adiabatic temperature change (ΔT). Considerable attention has been paid to bulk, thin films, and polymers materials, [10][11][12][13][14][15][16][17][18] and a lot of excellent results are obtained, such as PbZr 0.95 Ti 0.05 O 3 film with a ΔT ¼ 12 K under ΔE ¼ 480 kV cm À1 at 226 C, [7] BaTiO 3 single crystal with ΔT ¼ 0.90 K under ΔE ¼ 12 kV cm À1 at 129 C, [11] etc. Experiments have confirmed that outstanding ECEs are accompanied by the first-order phase transition (FPT) [7,11,12] and the diffuse phase transition (DPT).…”

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confidence: 99%

Large Room Temperature Electrocaloric Effect in KTa_1−xNb_xO₃ Single Crystal

Huang

Tian

Meng

et al. 2018

Physica Rapid Research Ltrs

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Component regulation has a significant influence on the ferroelectric structural phase‐transition characteristics such as the temperature (Tc) and the functional properties. Here, the electrocaloric (EC) properties in potassium tantalate niobate (KTa1−xNbxO3) single crystal are reported. The KTN43 (x = 0.43) single crystal exhibits an adiabatic temperature change of ΔT = 0.76 K at 15 kV cm−1 with both the first‐order and the diffuse phase transition performances near Tc. It represents a good solution for the two intractable contradictions for electrocaloric effect (ECE), namely that the large EC peak value prevents a low working temperature and a wide temperature span. It is shown that improving the Nb component in KTN single crystal can obviously elevate the EC properties. KTN shows good EC properties, including large adiabatic temperature change, low driving electric fields, large refrigeration capacity, working near room temperature and reversibility for all temperature range. These properties indicate that KTN is a promising EC material for practical application.

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“…oxyfluorides with the general chemical formulation (A + ) 2 A 0 MeO x F 6Àx (x: 0, 1, 2, 3) having elpasolite-cryolite structure (sp. gr.…”

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confidence: 99%