A direct electrocaloric effect (ECE) measurement system, based on a modified-differential scanning calorimeter (DSC), allowing the acquisition of both thermal (ECE, heat capacity) and electrical (P-E loops, leakage current) information simultaneously, was used to analyze 〈001〉-oriented PbMg1/3Nb2/3O3-30PbTiO3 single crystals. Different electric-field-induced phase transitions were identified on direct ECE measurements and confirmed by dielectric measurements. The strongest ECE (ΔTEC = 0.65 K) was measured for an applied electric field E = 10 kV/cm just above the temperature of depolarization. The direct ECE measurements were compared with indirect measurements obtained from dielectric polarization measurements versus electric field and temperature and a very good agreement was found. A region with negative ΔTEC was identified by both direct and indirect measurements. This phenomenon was attributed to the formation of a reversible field-induced phase transition towards a state with a different polar direction.
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The highly anisotropic electrocaloric effect, evidenced by both direct measurements and a descriptive theoretical model in lead‐free relaxor ferroelectric Sr0.75Ba0.25Nb2O6 single crystals, can be exploited by producing low‐cost grain‐oriented ceramics. Combined with the broad‐temperature‐range cooling regime provided by their polar nanoregions, these materials may be the key to future cost‐ and energy‐efficient solid‐state refrigeration.
Electrocaloric refrigeration is one of the most promising, environmentally-friendly technology to replace current cooling platforms-if a notable electrocaloric effect (ECE) is realized around room temperature where the highest need is. Here, we report a straightforward , onepot chemical modification of P(VDF-ter-TrFE-ter-CTFE) through the controlled introduction of small fractions of double bonds within the backbone that, very uniquely, decreases the lamellar crystalline thickness while, simultaneously, enlarging the crystalline coherence along the a-b plane. This increases the polarizability and polarization without affecting the degree of crystallinity or amending the crystal unit cell-undesirable effects observed with other approaches. Specifically, the permittivity increases by >35%, from 52 to 71 at 1 kHz, and ECE improves by >60% at moderate electric fields. At 40 C, an adiabatic temperature change >2 K is realized at 60 MVꞏm-1 (>5.5 K at 192 MVꞏm-1), compared to 1.3 K for pristine P(VDFter-TrFE-ter-CTFE), highlighting the promise of our simple, versatile approach that allows direct film deposition without requiring any post-treatment such as mechanical stretching or high-temperature annealing for achieving the desired performance. Enhanced Electrocaloric Response of Vinylidene Fluoride-based Polymers via One-Step Molecular Engineering
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