Electrocaloric effect in ferroelectric polymers

Lu, Sheng‐Guo; Rožič, B.; Zhang, Q. M.; Kutnjak, Zdravko; Pirc, R.

doi:10.1007/s00339-012-6830-9

Cited by 50 publications

(40 citation statements)

References 43 publications

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“…125). In other words, Equation (1) using the polarization as the order parameter under proper mechanical boundary conditions 24,25 may fail to describe the electrocaloric effect. Finally, a homemade calorimeter using a microfabricated resistance thermometer (integrated onto the substrate) was developed by Jia and Ju to provide direct measurement on electrocaloric effect in organic thick films.…”

Section: Specifically Designed Calorimetersmentioning

confidence: 99%

“…This approach can naturally include the boundary conditions and/or coupling to the strains (for example, in thin films) and therefore is a standard practice in this field. 11,24,25 However, in practical situations, precise determination of PðE; TÞ and its derivative @P @T E are challenging, especially for discontinuous first-order phase transitions, and cause several concerns (see Sections II B and Section II E). Moreover, the specific heat CðE; TÞ in Equation (1) is both temperature-and field-dependent.…”

Section: A Basic Thermodynamic Description Of Electrocaloric Refrigementioning

confidence: 99%

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

Liu

Scott

Dkhil

2016

Applied Physics Reviews

246

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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Section: Specifically Designed Calorimetersmentioning

confidence: 99%

Section: A Basic Thermodynamic Description Of Electrocaloric Refrigementioning

confidence: 99%

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

Liu

Scott

Dkhil

2016

Applied Physics Reviews

246

150

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“…However, only a few investigations have thus far been carried out with aim to gaining an understanding of secondary contribution to electrocaloric response of materials. An example is the work by Kutnjack and coauthors [1], who have estimated for PVDF-TrFE 55/45 mol % copolymer a secondary contribution of 26% to the overall electrocaloric effect. This value was predicted based on the assumption of a constant and electric field independent thermal expansion coefficient.…”

Section: Investigations Of Secondary Contribution To Electrocaloric Ementioning

confidence: 97%

“…Since ferroelectrics are also piezoelectrics, their dimensions change upon the application of an electric field which, in turn, contributes to the electrocaloric response of the material, i.e. secondary effect [1]. Knowledge of primary (at constant strain) and secondary contributions can offer valuable insights into the development of new electrocaloric materials and devices.…”

Section: Investigations Of Secondary Contribution To Electrocaloric Ementioning

confidence: 99%

Investigations of Secondary Contribution to Electrocaloric Effect in Relaxor PMN-PT Ceramic

Correia

Rokosz

2015

Ferroelectrics

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In this work, primary and secondary contributions to electrocaloric effect were investigated in a relaxor PMN-PT ceramic, by combining polarization and strain hysteretic measurements. Our results indicate that, although the ceramic shows a large electromechanical response, field-induced dimensional change (secondary effect) accounts for less than 19 % of the ceramic electrocaloric response over the 30-200 C temperature range. We believe that the method for the characterization of electrocaloric materials presented herein can provide valuable insights into the development of novel and optimized materials and heterostructures by tailoring primary and secondary contributions.

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“…For free-standing films, a previous approximate phenomenological model for uniaxial ferroelectrics 11 yielded an expression for the EC-induced entropy change per unit volume,…”

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confidence: 99%

Characterization of the electrocaloric effect and hysteresis loss in relaxor ferroelectric thin films under alternating current bias fields

Jia¹,

Ju²

2014

Applied Physics Letters

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We report characterization and analysis of the frequency-dependent temperature responses in thin films exhibiting the electrocaloric (EC) effect under AC bias fields using a high-precision lock-in technique. The temperature response detected by an embedded thin-film resistance thermometer is analyzed using the steady-periodic solutions of a 3D heat conduction model to extract the equivalent volumetric heat sources/sinks, which represent the combined effects of electrocaloric cooling/heating and hysteresis loss. The dependence of the measured heat source strengths on the bias field frequency and amplitude is consistent with our model prediction and independently measured dielectric properties. The volumetric heating rate due to hysteresis loss is estimated to be as much as 15% of the EC heating/cooling rates for solution-cast relaxor ferroelectric polymer films studied here. Our experimental approach enables a systematic study of the electrocaloric performance of thin films and deleterious impact of hysteresis loss.

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Electrocaloric effect in ferroelectric polymers

Cited by 50 publications

References 43 publications

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

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

Investigations of Secondary Contribution to Electrocaloric Effect in Relaxor PMN-PT Ceramic

Characterization of the electrocaloric effect and hysteresis loss in relaxor ferroelectric thin films under alternating current bias fields

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