Ferroelectric electrocaloric conversion in 0.75(PbMg_1/3Nb_2/3O₃)–0.25(PbTiO₃) ceramics

Abstract

This paper presents electrocaloric measurements on 0.75(PbMg1/3Nb2/3O3)–0.25(PbTiO3) ceramics. Reversible heat exchanged up to 0.15 J g−1 with an applied field of 1.35 kV mm−1 was obtained. The interpretation of this observation is based on direct polarization measurements. Starting from the integration along the electric field of the derivative of the polarization versus temperature, it was possible to predict the heat upon a decrease in electric field for values up to 3 kV mm−1. However the simulations differ from the experiments and the discrepancy is believed to be due to hysteresis in ferroelectric materials. Finally a practical limit of the use of ferroelectric 0.75(PbMg1/3Nb2/3O3)–0.25(PbTiO3) ceramics is evidenced through electric conductivity appearance when the electrothermal conversion is very high.