Polyurethane-based nanocomposite films were prepared by incorporating carbon-coated SiC nanowires (SiC@C) into the polymer matrix. Electric field-induced strain measurements revealed that a loading of 0.5 wt% SiC@C increased the strain level by a factor of 1.7 at a moderate field strength (6.5 V µm⁻¹). Current–electric field characteristics and the film thickness dependence of strain demonstrated that the improvement of the electromechanical response was linked to a more pronounced space charge effect in the nanocomposite than in the polymer host. DSC measurements revealed that the level of phase mixing in the PU matrix remained unchanged after SiC@C filling; hence, the nano-objects themselves acted as charge traps.

We investigated the structural, dielectric, piezoelectric, ferroelectric, and electrocaloric properties of the samarium doped (Na_0.5Bi_0.5)_0.94Ba_0.06TiO₃ (NBT-6BT) ceramic. X-ray diffraction and Raman spectra confirm the coexistence of the rhombohedral and tetragonal structures for a low amount of Sm (≤8 mol. %), while the compositions with a higher amount of Sm₂O₃ (11 mol. %) have a pseudocubic structure. The thermal dependency of the dielectric permittivity revealed two phase transitions from ferroelectric to antiferroelectric at low temperatures, then to paraelectric phase at higher temperatures. The substitution of NBT-6BT with 2 mol. % of Sm₂O₃ remarkably enhances the ferroelectric and the piezoelectric properties of the (Na_0.5Bi_0.5)_0.94Ba_0.06TiO₃ ceramic. Furthermore, a large electrocaloric effect $(\mathrm{\Delta }T=1.4\mathrm{K})$ was directly measured on the ceramic doped with 2 mol. % of Sm₂O₃ under an applied electric field of 50 kV/cm.

Very few studies have explored the elastocaloric effect of elastomers other than natural rubber (NR). The aim of the present article is thus to evaluate the elastocaloric properties of a thermoplastic polyurethane (TPU) in terms of microstructural characteristics and thermoelastic coupling. Calorimetric measurements showed two successive peaks at 240 K and 282 K, attributed to the crystallization and melting of soft segments, respectively. X-ray diffraction indicated that TPU exhibited a fully reversible strain-induced crystallization at room temperature. Thermomechanical experiments performed at different elongations revealed a minimum adiabatic temperature variation of about −8 K after retraction of a sample initially elongated at λ = 5. This is comparable to NR performances. However, for cycles carried out between λ = 1 and λ = 5, tensile stress/elongation curves showed a non-elastic behavior of TPU. A pseudo-elastic response was obtained for cyclic elongation when unloading was incomplete, in our case, when λ was between 3 and 5. The recorded peak-to-peak temperature variation decreased from 4.5 K to 3.3 K when the number of cycles was increased to 5000. Despite the fact that the issue of fatigue resistance for TPU needs to be addressed, this work opens new perspectives for studying the elastocaloric properties of various polyurethanes (whether crosslinked or thermoplastic) as well as other materials with a tendency for strain-induced crystallization, such as polychloroprene, hydrogenated acrylonitrile butadiene rubber, and others.

A BaTi_0.91Sn_0.08Zr_0.01O₃ (BTSZ) ceramic was prepared by a conventional solid-state reaction method. Its structural, dielectric, ferroelectric, and pyroelectric properties were carefully studied. The Rietveld refinement was used to characterize the structural proprieties of the synthesized ceramic. The microstructure was observed by scanning electron microscopy. Phase transitions observed in the temperature dependent dielectric permittivity (ε_r–T and tan δ–T) showed a transition close to room temperature, resulting in improved piezoelectric, pyroelectric and electrocaloric performance. In addition, it was found that an electric field poling process changed the character of ε_r–T and tan δ–T plots. Resonance modes in the polarized state, where maximum power transmission was achieved, were observed in the impedance spectrum. The extra-slim hysteresis loops revealed a relatively low coercive field and hysteresis loss related to the diffuse phase transition, which can significantly improve energy storage efficiency up to 75% at 100 °C. To characterize the electrocaloric effect (ECE), indirect and direct methods based on the thermodynamic approach were used. Both methods results showed good consistency and revealed a large ECE peak evolving along the phase diagram. Furthermore, pyroelectric figures of merit (FOMs) for voltage responsivity (F_v), current responsivity (F_i), energy harvesting (F_E), new energy harvesting and detectivity (F_d) were calculated. Finally, thermal energy harvesting (N_D) was determined by using the Olsen cycle. The obtained maximum N_D was 233.7 kJ m⁻³ when the Olsen cycle operated at 25–100 °C and 0–30 kV cm⁻¹. This study introduces not only a technique to produce a high performance ceramic for refrigeration devices, but also broadens the range of applications for BT-based lead-free ferroelectrics beyond actuators, sensors, and energy harvesting to solid-state cooling.