The electrocaloric effect is a novel solid-state refrigeration technology that is considered an option to replace traditional vapor compression refrigeration owing to its advantages, such as low cost, high coefficient of performance (COP), and miniaturization. Currently, the main limitation that hinders the application of electrocaloric refrigeration devices is the insufficient temperature change in materials exhibiting the single-chip electrocaloric effect. In device design, the use of a regenerative or series structure can increase the system temperature span to the level of engineering applications. This study introduces the concept, performance indicators, and current research achievements of thermal switch devices in a series of electrocaloric refrigeration devices. Using the principle of the electrocaloric effect, the adaptability of different types of thermal switches in electrocaloric refrigeration devices was analyzed, and the research results of regenerative and a series of electrocaloric refrigeration prototype devices were presented. Simulations and analyses of the impact of thermal switching devices on the performance of refrigeration devices were conducted using a series of electrocaloric refrigerators. We believe that the series structure is theoretically suitable for electrocaloric refrigeration devices. The use of the fast response speed and high thermal resistance of thermal switch devices driven by an electric field to drive the fluid medium can assist a series of electrocaloric refrigeration devices to address the current technological limitation and thus unleash the technical potential of electrocaloric refrigeration technology in various refrigeration systems.

The electrocaloric effect (ECE), known for its environmentally friendly characteristics, holds significant promise for advancing next-generation solid-state refrigeration technologies. Achieving a large ECE along with a wide working temperature range near room temperature remains a key developmental goal. In this study, we successfully obtained a substantial ECE of 1.78 K and an extensive working temperature range of 103 K (ΔT > 1.52 K) near room temperature in CaZrO₃-modified BaTiO₃ lead-free ferroelectric ceramics. Furthermore, this achievement was verified using direct methods. The piezoresponse force microscopy (PFM) results suggest that the broad temperature range is attributed to the formation of ferroelectric microdomains and polar nanoregions (PNRs). Furthermore, X-ray photoelectron spectroscopy (XPS) and ultraviolet‒visible (UV‒Vis) spectroscopy reveal a decrease in the oxygen vacancy concentration and an increase in the bandgap for higher CaZrO₃ doping levels. These changes synergistically enhance the maximum applied electric field, helping to achieve a high-performance ECE near room temperature. This research presents a straightforward and effective approach for achieving high-performance ECEs in BaTiO₃ lead-free ceramics, offering promising prospects for application in next-generation solid-state refrigeration technologies.

The electrocaloric effect (ECE) offers a pathway to environmentally sustainable and easily miniaturized refrigeration technology, positioning it as a front-runner for the next generation of solid-state cooling solutions. This research unveils a remarkable ECE in a finely tuned (Ba_0.86Ca_0.14)_0.98La_0.02Ti_0.92Sn_0.08O₃ ceramic, exhibiting a temperature shift (ΔT) of 1.6 K across more than 85% of the maximum ΔT (ΔT_max) and spanning an exceptionally wide operational range of 92 K. Our investigation on dielectric responses and ferroelectric polarization-electric field (P–E) loops suggests that the broad operational scope results from the fragmentation of extended ferroelectric domains into smaller domains and polar nano-regions (PNRs) supported by PFM analysis. Furthermore, the introduction of La enhances spontaneous polarization by significantly extending the maximum electric field that can be applied, facilitating high-performance ECE at ambient temperature. This study positions BaTiO₃-based lead-free ceramic as a sustainable alternative for addressing the cooling demands of modern electronic components, marking a significant stride toward next-generation solid-state refrigeration.

Solid-state cooling technology based on electrocaloric effect (ECE) has been advanced as an alternative to replace the vapour-compression approach to overcome the releasing of the global warming gases. However, the development in high ECE materials is still a challenge. In this work, polarization merging strategy was proposed to achieve a large ECE in xBa(Sn_0.07Ti_0.93)O₃–(1−x)Ba(Hf_0.1Ti_0.9)O₃ ferroelectric ceramics, where x = 0, 0.2, 0.4, 0.6, 0.8, and 1. Ba(Sn_0.07Ti_0.93)O₃ with an orthorhombic phase and Ba(Hf_0.1Ti_0.9)O₃ with a rhombohedral phase at room temperature were prepared beforehand as precursors, and phase-coexisted xBSnT–(1−x)BHfT ceramics were formed via a solid-state reaction approach. Phase coexisting structures were confirmed using the X-ray diffraction. The merged polarization was confirmed by the dielectric and ferroelectric properties. Optimal ECEs were obtained for 0.2BSnT–0.8BHfT ceramics, i.e., adiabatic temperature change ΔT = 2.16±0.08 K at 80 ℃ and 5 MV/m, and ΔT = 3.35±0.09 K at 80 ℃ and 7 MV/m.

Intra porous fibrous membranes have enhanced metal ionic adsorption and oil separation abilities than those of intra nonporous fibrous membrane. In this paper, we prepared highly intra porous fibrous poly (vinylidene fluoride) (PVDF) membranes using an innovated water-mediated electrospinning approach. FTIR-ATR and XRD techniques confirmed the conversion of non-polar α-phase to polar β-phase in electrospun membranes. The porous fibrous membrane M–16 had adsorbed oil almost 120% and metal adsorption around 15%, 12%, 5%, 13% respectively for Pb²⁺, Cd²⁺, Cu²⁺ and Zn²⁺, which are larger than the counterpart of nonporous M–18. The nonporous fibrous membranes have better peak to peak output voltage (V_p-V_p) 2 to 3 times than the porous fibrous membranes (M–16). The results show apparent potential applications in wastewater/oil spill treatment as well as piezoelectric sensors.

(Ba_1−xSr_x)(Mn_yTi_1−y)O₃ (BSMT) ceramics with x = 35, 40 mol% and y = 0, 0.1, 0.2, 0.3, 0.4, 0.5 mol% were prepared using a conventional solid-state reaction approach. The dielectric and ferroelectric properties were characterized using impedance analysis and polarization–electric field (P–E) hysteresis loop measurements, respectively. The adiabatic temperature drop was directly measured using a thermocouple when the applied electric field was removed. The results indicate that high permittivity and low dielectric losses were obtained by doping 0.1–0.4 mol% of manganese ions in (BaSr)TiO₃ (BST) specimens. A maximum electrocaloric effect (ECE) of 2.75 K in temperature change with electrocaloric strength of 0.55 K·(MV/m)^–1 was directly obtained at ~21 ℃ and 50 kV/cm in Ba_0.6Sr_0.4Mn_0.001Ti_0.999O₃ sample, offering a promising ECE material for practical refrigeration devices working at room temperature.

The effect of a N,N-dimethylformamide (DMF)/acetone solvent system (3:7, 4:6, 5:5, 6:4, 7:3) and spinning medium (air and water) on the membrane morphology and the structure-property relationship were investigated. A facile method was optimized to generate a porous, polymer-fiber membrane via the combinative effect of electrospinning and thermally inducing phase separation of the DMF/acetone (4:6) solvent system in a water medium. The attenuated total reflection (ATR) - Fourier transform infrared (FTIR) results showed an increased β-phase compared to the pristine poly(vinylidene fluoride) (PVDF). The XRD and DSC results further confirmed that the co-existing α- and β-phases in the pristine PVDF were converted into a unique β-phase in the electrospun membranes. In addition, the solvent uptake percentage of the DMF/acetone (4:6) solvent system in a water medium (540) is much greater than that in an air medium (320), and over two times better than that of commercial polyethylene (PE) membranes (190). Similarly, the discharge capacity of the PVDF membrane separator prepared with the DMF/acetone (4:6) solvent system in a water medium is higher than that of the air medium. This enhancement of solvent uptake might be due to the interconnected porous morphology present in the water medium.