Large electrocaloric effect and broad temperature span in BaTiO3 ceramics via phase coexistence strategy

Ferroelectrics, featuring a natural switchable polarization, have motivated immense interest due to their transformative potential in electronics, micromechatronics and electro-optics. Despite the remarkable advances achieved, the high coercive field required to reconfigure robust chemical bonds in traditional ferroelectrics fundamentally precludes their applications in next-generation energy-efficient devices. Herein, we present an innovative chemical bonding engineering approach to develop a hybrid metal halide ferroelectric, (iso-amylammonium)2CsGe2I7 (ICGI), which demonstrates ultra-low barrier ferroelectricity. Through enhancing the chemical bonding anisotropy via ns2 lone pairs stereochemical expression, the Ge-I bonding in ICGI adopts an asymmetrical pyramidal coordination geometry, which breaks structural inversion symmetry and results in a large spontaneous polarization up to 19.09 µC/cm2. Particularly, the smooth switching pathway refrained from abrupt breaking and reformation of weakened short-range bonding interactions results in a record-low coercive field < 0.35kV/cm (corresponding to switching energy < 0.0575 J/cm3), much lower than traditional ferroelectrics such as BaTiO3 (> 1.0kV/cm) and HfO2 (> 1000kV/cm). Furthermore, benefiting from the low barrier ferroelectricity, ICGI demonstrates a low electric field driven pronounced electrocaloric effect with an adiabatic ΔT/ΔE of 800 mK·cm/kV. This work encourages the targeted design of low barrier ferroelectrics, which sheds light on their applications in next-generation ultralow-power devices.

Enhanced electrocaloric effect in NaNbO3-based lead-free antiferroelectric ceramics

A growing number of cooling devices1-4 exploit large electrocaloric effects associated with a supercritically driven first-order ferroelectric phase transition in multilayer capacitors of PbSc0.5Ta0.5O3 (PST)5. However, these multilayer capacitors only operate above the room-temperature Curie temperature and require an energetically expensive 42-day anneal for high B-site order to maximize latent heat. Here we show that exaggerating valence mismatch through dilution with PbMg0.5W0.5O3 (PMW) maintains high B-site order and latent heat with no anneal, while disrupting dipolar order to reduce the Curie temperature as low as 230 K. Our multilayer capacitors of PST-PMW show supercritical electrocaloric effects of about 3 K across and well below room temperature owing to 17.1 V μm-1 fields we apply >107 times without breakdown. Using our multilayer capacitors in an ideal fluid regenerator and assuming work recovery yields cycle efficiencies of 70-90%. Taken together, our findings imply that multilayer capacitors of PST-PMW should now replace multilayer capacitors of PST in electrocaloric prototypes to permit electrocaloric refrigeration.

State-of-the-art electrocaloric cooling prototypes rely on the conventional electrocaloric effect of ferroelectric lead scandium tantalate (PbSc0.5Ta0.5O3, PST), which peaks near room temperature. Here, we demonstrate that A-site calcium doping in highly ordered PST modifies its phase transitions and enables precise tuning of the electrocaloric response. The transition temperature shifts down to 258 K and up to 319 K, depending on Ca concentration. Calorimetry under electric field, electrical polarization loops, and piezoresponse force microscopy reveal the emergence of an intermediate antiferroelectric phase stabilized for Ca ≥ 2%. These results are supported by first-principles calculations. We observe conventional electrocaloric effect for Ca ≤ 2% and inverse electrocaloric effect at higher doping (≥ 2%). Under an applied field of 110 kV cm−1, Ca-doped PST exhibits an adiabatic temperature change of 2 K over a range from 263 K to 353 K. Such Ca-doped PST compounds could be used to expand the temperature range of PST below the freezing point of water. Our results offer a pathway to cascaded electrocaloric cooling devices with extended operating spans.

Aging and enhanced electrocaloric effect in (Na0.5Bi0.5)TiO3-BaTiO3 ceramics

Optimization of electrocaloric effect in PIN-PMN-PT transparent ceramics via relaxor ferroelectric phase transition

Electrocaloric (EC) solid-state cooling technology is attracting interest as a versatile solution for energy-efficient thermal regulation in industrial and electronic applications. Ferroelectric materials, characterized by significant polarization and entropy variations in response to electric fields, offer small, environmentally sustainable cooling systems suitable for integration into sophisticated devices. Recent studies highlight the necessity of lead-free electrochemical materials to comply with ecological and regulatory standards. The article offers a thorough examination of the thermodynamic concepts that regulate EC refrigeration and emphasizes advancements in Pb-free materials, encompassing bulk ceramics, single crystals, thin and thick films, multilayer structures, and polymers. Emphasis is placed on compositional engineering and structural design methodologies that improve electrochemical performance while guaranteeing mechanical dependability for industrial applications. The discussion encompasses modeling and simulation endeavors concerning BaTiO₃ (BT), BaSrTiO₃ (BST), and P(VDF-TrFE) copolymers, as well as novel methodologies for scalable device integration. Ultimately, prospective avenues are delineated for the advancement of multifunctional electrochemical materials and composites that integrate temperature management with structural and energy capabilities for next-generation industrial and electronic systems.

Ferroelectric and antiferroelectric thin and thick films with strong electrocaloric (EC) responses are attractive for solid-state cooling. In this study, 0.75PbMg1/3Nb2/3O3–0.25PbTiO3 (PMN-25PT) relaxor ferroelectric thin films deposited on LSAT substrates by pulsed laser deposition exhibit a giant negative EC effect near 150 °C, with a maximum temperature change of −38.3 K and an entropy change of −29.4 J kg−1 K−1. A large positive EC effect is also observed near 120 °C, yielding ΔT = 33.4 K and ΔS = 27.5 J kg−1 K−1, comparable to the best reported values. The films show nanoscale columnar grains that promote polar nanoregions, leading to high polarization, large dielectric breakdown strength, and a diffuse, frequency-dependent dielectric response. Polarization–electric field loops measured from 30 °C to 190 °C reveal the excellent thermal stability of energy storage, which remains robust after 108 charge–discharge cycles. Moreover, the films demonstrate efficient harvesting of low-grade waste heat, achieving an energy conversion density of ∼18.7 J cm−3 per cycle over 0–2.5 MV cm−1 and a wide temperature range of 30–140 °C, as evaluated using pyroelectric Olsen cycles. These results highlight PMN-25PT thin films as promising candidates for advanced energy storage and electrocaloric cooling applications.

Electrocaloric effect of hafnium substituted barium titanate with diffused phase transition measured through both indirect and direct methods

Abstract With the global surge in refrigeration demand, developing efficient, environmentally friendly solid-state refrigeration technologies is urgent. Polymer materials leveraging the electrocaloric effect (ECE) are promising alternatives to traditional vapor compression refrigeration, due to their zero global warming potential and flexibility. This review summarizes progress in polymer-based electrocaloric (EC) material composites from material design to device integration, emphasizing multiscale synergistic design as the core strategy to address polymers' inherent low thermal conductivity and high operating electric fields. We discuss ECE regulation mechanisms and synergistic effects across scales, molecular (defect engineering, high-entropy design), mesoscale (interface engineering), and macroscale (film thickness, external field control). Key challenges (low thermal conductivity, high operating fields) are analyzed, and future work should focus on precise interface engineering and multiscale structural design to advance polymer electrocaloric coolers from lab to commercialization.

This study investigates the electrocaloric effect (ECE) in a poly(vinylidenefluoride‐trifluoroethylene) (P(VDF‐TrFE) (70/30)) copolymer, as well as and its 0–3 composites with containing 10 and 20 vol% of Ba(Ca, Zr, Ti)O 3 (BZCT) as ceramic fillers, including a ternary variant with 2 vol% of polyaniline (PANI). The films were prepared by solution casting and characterized by using X‐ray diffraction (XRD), Fourier‐transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), dielectric measurements, and polarization‐electric (P–E) hysteresis loops. Indirect ECE analysis revealed negative adiabatic temperature changes (Δ T ), peaking at −11 K at 25°C for pure P(VDF‐TrFE), −4.5 K at 75°C for 10 vol% BZCT, and −9.0 K at 60°C for 10 vol% BZCT/PANI under 1200 kV/cm electric fields of 1200 kV/cm. The observed shifts in peak Δ T are attributed to thermal hysteresis, interfacial polarization, strain‐mediated coupling, and the conductivity‐enhancing charge mobility of PANI. These lead‐free composites demonstrate the potential for energy‐efficient and, compact cooling technologies.

Electrocaloric and energy storage properties of barium stannate titanate system: A multifunctional approach

Simultaneous enhancement of operating temperature range and adiabatic temperature change in the electrocaloric effect of (1-x)PST-xPT ceramics

Compositionally engineered core@shell Ba(Zr, Ti)O3 for concurrent giant electrocaloric effect and ultra-wide operational window

Ferroelectric (FE) ultrathin films tend to favor a homogeneous polar state at strong interfacial bound charge screening conditions. Reducing screening parameter (β) may induce topological textures such as vortices, labyrinth stripes, and skyrmion bubbles (sk-bs). Here, we exploreβ- and temperature-induced phase transitions of polarization reversal in FE PbZr0.2Ti0.8O3(PZT) thin films using phase-field simulations under a 1% compressive strain. The results unveil a phase diagram comprising polarization reversal, hysteresis loop and topological structures. At room temperature, a phase transition from FE to antiferroelectric-like (AFE*) state occurs atβ∼0.53. At increasing temperatures, the FE and AFE* phases convert to a paraelectric state and form a tricritical point atβ∼0.78 andT∼ 770 K. Notably, at the phase boundary, a coexistence region of uniform polarization and isolated sk-bs emerges in a narrow screening range, which can be modulated by an applied electric field. Moreover, simulations of thermal effects on the FE to AFE* phase transition via the indirect method reveal a large electrocaloric effect around room temperature at low electric fields. Our findings uncover rich phenomena and elucidate underlying mechanisms in FE thin films, which hold promise for advanced device applications.

Abstract Addressing the urgent demands for intelligent, miniaturized, and efficient thermal management in modern electronics, alongside the energy and environmental constraints, the development of compact and high‑performance cooling systems has become imperative. The electrocaloric (EC) effect, which enables reversible entropy and temperature changes in dielectric materials through electric‑field‑controlled polarization, offers distinct advantages including high efficiency, fast response, and ease of integration. This review outlines the thermodynamic principles and surveys the evolution of EC thermal management devices. Ceramic-based EC devices exhibit strong potential for high‑power applications due to their high thermal conductivity and thermal stability, while polymer-based EC devices are suited to wearable and flexible integration because of their mechanical compliance and processability. This review further contrasts the design, actuation, and application profiles of these platforms. Despite notable progress, challenges remain in long‑term stability, multi‑physics coupling, miniaturized integration, and environmental adaptability. Advances in material understanding, device design, and intelligent system control will position EC technology as a key enabler of efficient, compact, and sustainable next‑generation thermal management.

Almost 70 years after the discovery of ferroelectricity of thiourea – one of the earliest organic crystal structures to be studied – this work unveils new electrocaloric effects in the cryogenic region that can be enhanced by mechanical pressure.

The development of high-performance electrocaloric effect (ECE) is of great importance for local refrigeration (such as chip and wearable electronics cooling, etc.). However, how to simultaneously achieving both a large...

Effect of perpendicular defect dipoles on phase transition and electrocaloric effect of BaTiO3