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Published on: August 15, 2015
Large Electrocaloric Responsivity and Energy Storage Response in the Lead-Free Ba(GeTi1-)O3 Ceramics
Bouchra Asbani1,2, Yaovi Gagou1, Said Ben Moumen3
1Laboratoire de Physique de La Matière Condensée (LPMC), Université de Picardie, Jules Verne, 33 rue Saint-Leu, CEDEX 1, 80039 Amiens, France.
Abstract:
Ferroelectric property that induces electrocaloric effect was investigated in Ba(GeTi1-)O3 ceramics, known as BTGx. X-ray diffraction analysis shows pure perovskite phases in tetragonal symmetry compatible with the P4mm (No. 99) space group. Dielectric permittivity exhibits first-order ferroelectric-paraelectric phase transition, confirmed by specific heat measurements, similar to that observed in BaTiO3 (BTO) crystal. Curie temperature varies weakly as a function of Ge-content. Using the direct and indirect method, we confirmed that the adiabatic temperature change ΔT reached its higher value of 0.9 K under 8 kV/cm for the composition BTG6, corresponding to an electrocaloric responsivity ΔT/ΔE of 1.13 × 10-6 K.m/V. Such electrocaloric responsivity significantly exceeds those obtained so far in other barium titanate-based lead-free electrocaloric ceramic materials. Energy storage investigations show promising results: stored energy density of ~17 mJ/cm3 and an energy efficiency of ~88% in the composition BTG5. These results classify the studied materials as candidates for cooling devices and energy storage applications.
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