Wide Electrocaloric Temperature Range Induced by Ferroelectric to Antiferroelectric Phase Transition

Abstract

The ferroelectric (FE) to antiferroelectric (AFE) phase transition tuning the temperature range of electrocaloric (EC) effects was investigated using phenomenological Landau–Devonshire theory. Contrary to ferroelectric to paraelectric (PE) phase transitions for electrocaloric effects, the ferroelectric to antiferroelectric phase transition was adopted to obtain large entropy changes under an applied electric field in a Sm-doping BiFeO3 system. In addition, the doping composition and hydrostatic pressure was observed to tune the ferroelectricantiferroelectric–paraelectric phase transition temperatures and broaden the operating temperature range of electrocaloric effects. The optimal wide temperature range of ~78 K was observed at 3 GPa compressive hydrostatic pressures and 0.05 Sm-doping BiFeO3. The present study paves the way to designing high efficiency cooling devices with larger operating temperature spans.

Understanding electrocaloric cooling of ferroelectrics guided by phase‐field modeling

“…In addition to strain, the ECEs of ferroelectric materials are also affected by the applied stress, such as thermal stress, 111 surface tension, 78 uniaxial stress, 61,75,88,89,112 and hydrostatic pressure. 38,[113][114][115] Similar to the strain, the stress also impacts the domain structure change of the ferroelectric material, thereby tuning the ECE of the material. In recent years, several researchers have focused on explore this field.…”

“…When hydrostatic pressure of 1.0 GPa is imposed to MDABCO, the T C decreases from 448 to 293 K, but the Δ S /Δ E and Δ T /Δ E diminish from 18 J m kg −1 K −1 MV −1 and 8.06 K m MV −1 to 7.5 J m kg −1 K −1 MV −1 and 2.2 K m MV −1 (Δ E = 2 MV m −1 ), respectively. Moreover, Sun et al 115 . found that the hydrostatic pressure can induce the appearance of the AFE phase, and make BFO undergo a FE–AFE–PE phase transition process, thereby widening the temperature range of ECE.…”

Is Barocaloric an Eco-Friendly Technology? A TEWI Comparison with Vapor Compression under Different Operation Modes

“…The solid-state nature of the refrigerants avoids that a system based on barocaloric cooling or heat pumping could contribute in the accidental release of refrigerants in the atmosphere, contrary to what happens with vapor compression whose refrigerants have a fluid nature. Barocaloric is counted among the caloric cooling and heat pumping class of technologies, all having the common denominator of being based on solid-state refrigerants exhibiting a caloric effect [7] (magnetocaloric, electrocaloric, elastocaloric and barocaloric effect, in dependence of the nature of the external stimulus) [8][9][10][11][12][13].…”

Enhancing the Heat Transfer in an Active Barocaloric Cooling System Using Ethylene-Glycol Based Nanofluids as Secondary Medium

“…In this paper, we numerically investigate the effect on heat transfer of working with nanofluids as auxiliary fluids in an active barocaloric refrigerator operating with a vulcanizing rubber. The results reveal that, as a general trend, adding 10% of copper nanoparticles in the water/ethylene-glycol mixture carries to +30% as medium heat transfer enhancement.Energies 2019, 12, 2902 2 of 15 effects (ECE) [20][21][22], and mechanical fields provoke elastocaloric (eCE) [23] or barocaloric effects (BCE) [24], respectively, as consequences of stretching or of hydrostatic pressure application.Caloric cooling is classified as environmentally friendly because it employs solid-state materials as refrigerants that do not directly impact global warming since they do not disperse in the atmosphere, as confirmed by a certain number of investigations [25][26][27][28] that asserted the eco-friendliness of all the techniques belonging to magneto- [29,30], electro-[31,32], elasto-[33,34], and baro-caloric [35] cooling.The reference and well-established systems for caloric cooling are based on the active caloric regenerative refrigeration (ACR) cycle, a thermodynamic Brayton-based cycle in which the caloric solid-state material acts as both the refrigerant and the regenerator, thus recovering heat fluxes through the help of an auxiliary fluid that vehiculates them with the final purpose of subtracting heat from the cold heat exchanger (and therefore the cold environment) [36]. To improve the efficiency of a caloric cooler, the ACR system works with the optimal operative parameters (such as the geometry of the regenerator, the fluid velocity, and the frequency of the cycle) [37-39] but the bottleneck is employing materials due of high caloric effect in the temperature range toward the application is devoted to [40].…”

“…Energies 2019, 12, 2902 2 of 15 effects (ECE) [20][21][22], and mechanical fields provoke elastocaloric (eCE) [23] or barocaloric effects (BCE) [24], respectively, as consequences of stretching or of hydrostatic pressure application.…”