Large Electrocaloric Responsivity and Energy Storage Response in the Lead-Free Ba(Ge x Ti1- x)O3 Ceramics

Bouchra Asbani; Yaovi Gagou; Said Ben Moumen; Jean-Luc Dellis; Abdelilah Lahmar; M'Barek Amjoud; Daoud Mezzane; Mimoun El Marssi; Brigita Rozic; Zdravko Kutnjak

doi:10.3390/ma15155227

Large Electrocaloric Responsivity and Energy Storage Response in the Lead-Free Ba(Ge _x Ti_{1- x})O₃ Ceramics

Materials (Basel). 2022 Jul 28;15(15):5227. doi: 10.3390/ma15155227.

Authors

Affiliations

¹ Laboratoire de Physique de La Matière Condensée (LPMC), Université de Picardie, Jules Verne, 33 rue Saint-Leu, CEDEX 1, 80039 Amiens, France.
² Unit of Dynamics and Structure of Molecular Materials-UDSMM (EA 4476), MREI-1, Université du Littoral Côte d'Opale, 59140 Dunkerque, France.
³ IMED-Lab, Department of Applied Physics, Faculty of Sciences and Techniques, Cadi Ayyad University, P.O. Box 549, Marrakesh 40000, Morocco.
⁴ Jozef Stefan Institute, Jamova Cesta 39, 1000 Ljubljana, Slovenia.

Abstract

Ferroelectric property that induces electrocaloric effect was investigated in Ba(Ge_xTi_1-x)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.

Keywords: BGT; ceramics; electrocaloric; energy storage; ferroelectric.

Grants and funding

This work was supported financially by The Ministry for Europe and Foreign Affairs (MAEDI) via PHC Carlos Finlay project No 47075NF and University of Picardie Jules Verne via S2R Action 3.