Indirect and direct electrocaloric measurements of (Ba1-xCax)(Zr0.1Ti0.9)O-3 ceramics (x=0.05, x=0.20)
Résumé
Electrocaloric effect in lead-free (Ba1-xCax) (Zr0.1Ti0.9)O-3 ceramics (with x = 0.05 and x = 0.20) has been investigated by using two different indirect methods. In the first classic approach, the electrocaloric temperature change (Delta T) was calculated from the Maxwell relation based on measured P-E hysteresis loops recorded at different temperatures. In the second approach, the Delta T was calculated from the Maxwell relation based on pyroelectric current measurements. The advantage of such approach is that it enables direct determination of the pyroelectric coefficient, which should be otherwise calculated from the hysteresis loops in the classic approach. Direct method was finally used for verification of the obtained results. Good agreement between methods was found near the cubic-to-tetragonal phase transition temperature with a significant electrocaloric responsivity of Delta T/Delta E = 0.30 K mm/kV for the composition x = 0.05 obtained by direct method. (c) 2016 Elsevier B.V. All rights reserved.