Present and future caloric refrigeration and heat-pump technologies

Kitanovski, Andrej; Plaznik, Uroš; Tomc, Urban; Poredoš, Alojz

doi:10.1016/j.ijrefrig.2015.06.008

Cited by 232 publications

(126 citation statements)

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“…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.…”

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confidence: 99%

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

Liu

Scott

Dkhil

2016

Applied Physics Reviews

234

150

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It has been ten years since the discovery of the giant electrocaloric effect in ferroelectric materials showed that it is possible to employ this effect for substantial cooling applications. This last decade has been marked by increasing research interest, especially in characterizing and measuring the electrocaloric effect using both the so-called indirect and direct approaches. In this context, a comprehensive summary and careful reexamination of these approaches are very timely and of great importance to justify the assumptions used in different measurement techniques. This review is therefore dedicated to cover recent important and rapid advances from both the indirect and direct measurements and provides critical insights relevant for quantifying the electrocaloric effect. It involves electrocaloric materials from normal ferroelectrics, antiferroelectrics, and relaxors, and it fundamentally focuses on how the electrocaloric entropy changes in response to electric field in these typical electrocalorics. The article addresses recent developments, especially during the past three years, such as technical selection of proper polarization-electric field loops, negative electrocaloric effect in antiferroelectrics and relaxors, the controversial debate on the indirect method in relaxors, the important role of field dependence of specific heat, kinetic factors, and so on. Moreover, this review also is concerned with extracting reliable data by direct measurements. Four typical techniques and devices used recently, such as thermocouples, differential scanning calorimeters, specifically designed calorimeters, and scanning thermal microscopy, are briefly reviewed, while infrared cameras are emphasized. We hope that our review will not only provide a useful background to understand fundamentally the electrocaloric effect and what one really measures but also may act as a practical guide to exploit and develop electrocalorics towards the design of suitable devices. Published by AIP Publishing. [http://dx

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confidence: 99%

“…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.…”

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confidence: 99%

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

Liu

Scott

Dkhil

2016

Applied Physics Reviews

234

150

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“…[2][3][4][5] Investigations into the solid-state first order transition are now focused on various materials driven by not only the magnetic field but also the mechanical and the electric fields. [6][7][8][9] In the first-order phase transition, the caloric phenomena were observed as a consequence of the generation of latent heat. The first-order phase transition occurs at the critical temperature T C when the free energy of an initial state F i equals to that of a final state F f (F f = F i ).…”

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confidence: 99%

Relation between paramagnetic entropy and disordered local moment in La(Fe0.88Si0.12)13 magnetocaloric compound

Fujita

2016

APL Materials

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The paramagnetic fluctuations are investigated in La(Fe0.88Si0.12)13. The disordered local moment (DLM) is represented by the first principle calculations. With a reduction of the volume, the DLM amplitude decreases gradually. In the temperature dependence of electrical resistivity ρ under hydrostatic pressure, an upturn in the variation of ρ in the paramagnetic state was observed with decreasing temperature, which is originated from the Curie-Weiss-type DLM fluctuations. In the vicinity of the critical pressure for disappearance of the DLM, the variation of ρ as a function of log(T) was observed.

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“…[2] Such effects have been widely utilized in a range of applications; pyroelectrics for infrared imaging, radiometry, electron emission, [3,4] and for the recovery of electrical energy from waste heat [5,6]; and electrocalorics for environmentally-friendly, solid-state cooling technologies (i.e., low-power, gaseous refrigerant-free, etc.). [7,8] The pyroelectric coefficient π is typically characterized by measuring the pyroelectric current (i P = Aπ dT dt , where A is the area of the capacitor and dT dt the temperature ramp rate) generated in response to a known temperature transient. Most techniques used to measure pyroelectric properties were developed to probe bulk ceramics or single crystals, including laserinduced heating [9] and continuous ramp-rate heating studies.…”

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confidence: 99%

Direct Measurement of Pyroelectric and Electrocaloric Effects in Thin Films

et al. 2017

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Understanding of polarization-heat interactions in pyroelectric and electrocaloric thin-film materials requires that the electrothermal response is reliably characterized. While most work, particularly in electrocalorics, has relied on indirect measurement protocols, here we report a direct technique for measuring both pyroelectric and electrocaloric effects in epitaxial ferroelectric thin films. We demonstrate an electrothermal test platform where localized high-frequency (∼ 1 kHz) periodic heating and highly-sensitive thin-film resistance thermometry allow direct measurement of pyrocurrents (< 10 pA) and electrocaloric temperature changes (< 2 mK) using the "2-omega" and an adapted "3-omega" technique, respectively. Frequency-domain, phase-sensitive detection permits extraction of pyrocurrent from the total current, which is often convoluted by thermally-stimulated currents. The wide frequency range measurements employed in this study further show the effect of secondary contributions to pyroelectricity due to the mechanical constraints of the substrate. Similarly, measurement of the electrocaloric effect on the same device in the frequency-domain (∼ 100 kHz) allows decoupling of Joule heating from the electrocaloric effect. Using one-dimensional, analytical heattransport models, the transient temperature profile of the heterostructure is characterized to extract pyroelectric and electrocaloric coefficients.

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Present and future caloric refrigeration and heat-pump technologies

Cited by 232 publications

References 50 publications

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

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

Relation between paramagnetic entropy and disordered local moment in La(Fe0.88Si0.12)13 magnetocaloric compound

Direct Measurement of Pyroelectric and Electrocaloric Effects in Thin Films

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