Antiferroelectric thin films are demonstrated as a new class of giant electrocaloric materials that exhibit a negative electrocaloric response of about −5 K near room temperature. The giant negative ...electrocaloric effect may open up a new paradigm for light, compact, reliable, and high‐efficiency refrigeration devices.
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(Pb0.97La0.02)(Zr x Sn0.94–x Ti0.06)O3 (PLZST) antiferroelectric ceramics with x = 0.75–0.90 have been fabricated and found to be a novel electrocaloric material system with a giant negative ...electrocaloric effect (ΔT = −11.5 K) and a large electrocaloric strength (|ΔT/ΔE| = 0.105 K cm kV–1) near room temperature. Additionally, the PLZST antiferroelectric ceramic also exhibits a large positive electrocaloric effect around the Curie temperature. The giant negative effect and the coexistence of both positive and negative electrocaloric effects in one material indicate a promising possibility to develop mid- to large-scale solid-state cooling devices with high efficiency.
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Solution‐processable ferroelectric polymer nanocomposites are developed as a new form of electrocaloric materials that can be effectively operated under both modest and high electric fields at ...ambient temperature. By integrating the complementary properties of the constituents, the nanocomposites exhibit state‐of‐the‐art cooling energy densities. Greatly improved thermal conductivity also yields superior cooling power densities validated by finite volume simulations.
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The first experimental evidence for a giant, conventional barocaloric effect (BCE) associated with a pressure‐driven spin crossover transition near room temperature is provided. Magnetometry, neutron ...scattering, and calorimetry are used to explore the pressure dependence of the SCO phase transition in polycrystalline samples of protonated and partially deuterated FeL2BF42 L = 2,6‐di(pyrazol‐1‐yl)pyridine at applied pressures of up to 120 MPa (1200 bar). The data indicate that, for a pressure change of only 0–300 bar (0–30 MPa), an adiabatic temperature change of 3 K is observed at 262 K or 257 K in the protonated and deuterated materials, respectively. This BCE is equivalent to the magnetocaloric effect (MCE) observed in gadolinium in a magnetic field change of 0–1 Tesla. The work confirms recent predictions that giant, conventional BCEs will be found in a wide range of SCO compounds.
A giant barocaloric effect is found at low pressures in a near‐room‐temperature spin‐crossover molecular crystal. Structural data obtained by neutron diffraction are correlated with magnetic data and heat‐capacity studies under hydrostatic pressure. This first experimental study of the barocaloric potential of spin‐crossover compounds provides motivation for a wider examination of the material class.
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Hafnia (HfO2)‐zirconia (ZrO2) solid solution films show giant positive (ΔT = 13.4 K) and negative (ΔT = −10.8 K) electrocaloric effects that can be simply controlled by tuning the Hf/Zr ratio. It is ...expected that the combination of the electrocaloric effects with opposite signs in this lead‐free, simple, binary oxide can significantly improve the efficiency of electrocaloric cooling.
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More than 55% of electronic failures are caused by damage from localized overheating. Up to now, there is still no efficient method for targeted temperature control against localized overheating. ...Although some existing thermal management devices handle this issue by full coverage cooling, it generates a lot of useless energy consumption. Here, a highly efficient pixel‐matrix electrocaloric (EC) cooling device is reported, which can realize a targeted and differential thermal management. The modified poly(vinylidene fluoride‐tertrifluoroethylene‐chlorofluoroethylene) reaches a large adiabatic temperature change of 7.8 K and is more suitable for thermal transfer and electrostatic actuation at high frequencies. All active pixels in the EC cooling device exhibit a stable temperature span of 4.6 K and a heat flux of 62 mW cm‐2, which is more than twice that of the one‐layer EC device. Each refrigeration pixel can be independently controlled and effectively cooled down the localized overheating site(s) in situ. The surface temperature of the simulated central processing unit decreases by 33.2 K at 120 s after applying this EC device. Such a compact, embeddable, low cost, and active solid‐state pixel‐matrix cooling device has great potential for localized overheating protection in microelectronics.
A highly efficient pixel‐matrix electrocaloric (EC) cooling device is demonstrated on which each refrigeration pixel can be independently controlled and can effectively cool down the localized overheating on microelectronics in situ as needed. All active pixels in the EC cooling device exhibit a stable temperature span of 4.6 K and a heat flux of 62 mW cm‐1.
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7.
Electrocaloric Coolers: A Review Torelló, Alvar; Defay, Emmanuel
Advanced electronic materials,
June 2022, Volume:
8, Issue:
6
Journal Article
Peer reviewed
Open access
Since the discovery of giant electrocaloric effects, researchers are intensively studying electrocaloric cooling as an alternative to vapor compression systems to develop more efficient heat pumps ...and mitigate climate change. Endorsed by its direct use of electricity, easy‐handling, and compact design, recent advancements in the performance of electrocaloric coolers have finally displayed temperatures comparable to similar competing technologies, and the topic has regained attention and interest. In this work, the design, performance, and working principles of all electrocaloric prototypes before the year 2021 are reviewed, and hints and guidelines are given for future works to bring the development of these devices one step closer to real applications.
Electrocaloric cooling is a promising alternative to vapor compression systems thanks to its zero global warming potential and its high energy efficiency. Herein, recent advancements on the design, working principles, and performances of electrocaloric coolers are reviewed and considered. The work provides hints and guidance to help future works bring these devices closer to real applications.
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Compact solid‐state refrigeration systems that offer a high specific cooling power and a high coefficient of performance (COP) are desirable in a wide range of applications where efficient and ...localized heat transfer is required. Here, a double‐unit electrocaloric (EC) polymer‐based refrigeration device with high intrinsic thermodynamic efficiency is demonstrated using a flexible EC polymer film with improved performance by doping plasticizer and an electrostatic actuation mechanism. The double‐unit refrigeration device achieves a large temperature span of 4.8 K, which is 71% higher than that of the single‐unit device. A specific cooling power of 3.6 W g−1 and a maximum COP of 8.3 for the cooling device are produced. The surface temperature of a central processing unit (CPU) cooled by an active EC device is 22.4 K lower than that of the CPU cooled in air. The highly efficient and compact EC cooling device demonstrated here not only leapfrogs the performance of existing solid‐state cooling technologies, but also brings solid state cooling closer to reality for a variety of practical applications that require compact or mechanically flexible refrigeration.
Electrocaloric cooling technology provides an effective alternative cooling plan for thermal regulation of microelectronics. Plasticizer modification effectively improves intrinsic electrocaloric performance of electrocaloric polymers. The modified electrocaloric polymer‐based refrigeration device with a maximum temperature span of 4.8 K has a high cooling efficiency. There is a 21.7 K temperature drop in a running central processing unit cooled by the electrocaloric refrigeration device.
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Hysteresis phenomena, including both electrical and thermal types, are essential to ferroelectric materials. The former, known as polarization‐electric field hysteresis, has been intensively studied ...in a wide range of ferroelectric materials. However, relevant experimental evidence on thermal hysteresis remains limited, especially in ferroelectric polymers, even though thermal hysteresis is crucial to the caloric effect, which is usually the largest near the phase transition. Here, the thermal hysteresis behavior in ferroelectric polymers is studied in terms of temperature‐dependent polarization upon heating and cooling. In contrast to common belief, a negative thermal hysteresis is observed in relaxor ferroelectric polymers, which is probably due to local stabilization of ferroelectric distortion induced by electric field. Using the polymer blend as a platform, it is further shown that the negative thermal hysteresis arises at the disappearance of long‐range ferroelectric distortion and the thermal hysteresis behavior may be effectively controlled through the blend approach. This study not only provides deeper insights into electrocaloric effect in ferroelectric polymers but also offers an approach to study the critical phenomenon in a ferroelectric system.
Negative thermal hysteresis behavior is observed in relaxor ferroelectric polymers, which is attributed to the electric‐field‐induced stabilization of local polarization. This study may open a new route to study the critical phenomenon in ferroelectric polymers and effectively tune the thermal hysteresis through a polymer blend approach.
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•High-efficiency cooling was realized by changing twist in a PVDF fiber.•Reversible crystal structure transformation was found during cooling.•An inverse twistocaloric cooling was ...realized for a heterochiral PVDF coil.•A strain sensitive mechanothermochromic fiber was demonstrated.
Developing new cooling strategies of solid-state cooling materials is highly desired in order to meet the high energy demand and new application scenarios for multicaloric cooling. Polyvinylidene difluoride (PVDF) is a typical ferroelectric polymer that shows electrocaloric effect, and general strategies for improving the cooling performance of PVDF-based polymers include material composition design, device optimization, etc. In this work, cooling was realized by changing twist of PVDF fibers. Cooling of −1.1 K was achieved by twist removal from a PVDF fiber, and −3.0 K cooling was realized by stretch release of a self-coiled PVDF fiber. During twist insertion and removal of the PVDF fiber, reversible transformation of crystal structure from orthorhombic to monoclinic phase was observed, which was ascribed as the origin of such twist-based cooling effect. Both coil stretching and releasing can realize cooling by using opposite and the same chirality of fiber twisting and coiling, respectively. A strain sensitive mechanothermochromic fiber was demonstrated to show different colors during stretching and releasing of a PVDF coil. The current research provides new era for improving the performance and finding new applications for PVDF-based cooling.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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