Electrocaloric properties of 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 ceramics

The electrocaloric (EC) effect is a conversion of electrical energy to heat and may be defined as an adiabatic and reversible temperature change that occurs in a polar material upon external electric field. The aim of our work was to prepare 0.7Pb(Mg_1/3Nb_2/3)O₃-0.3PbTiO₃ (0.7PMN-0.3PT) ceramics and to study the EC temperature change (ΔT) vs. applied electric field and temperature. For the synthesis of the 0.7PMN-0.3PT bulk ceramics, PbO, MgO, TiO₂ and Nb₂O₅ were used. The homogenized, stoichiometric powder mixtures were mechanochemically activated in a high-energy planetary mill, and milled in an attrition mill in isopropanol. The powder compacts were sintered at 1200 °C for 2 h in double alumina crucibles in the presence of the packing powder. The ceramic was single phase perovskite, with the relative density of 97 % and a uniform microstructure with the median grain size of 1.0 μm ± 0.5 μm. In order to study the EC effect, a high resolution calorimeter was used. The observed magnitudes of the EC effect confirmed the existence of a large EC effect in this material. A characteristic peak of AT as a function of the electric field was observed near the critical point, with the AT of 2.7 K at 90 kV/cm and 430 K.