IMF2017

The electrocaloric (EC) effect is defined as the change in entropy and, consequently, in the temperature of a dielectric material due to the electric-field-induced changes in the polar states. The 0.9Pb(Mg_1/3Nb_2/3)O₃–0.1PbTiO₃ (PMN-10PT) relaxor ceramic is one of the candidate EC materials due to its excellent dielectric properties, such as high dielectric permittivity, large change of polarization with temperature and low hysteresis losses. The EC temperature changes ΔT_EC which are large enough for possible applications are achieved at electric field amplitudes well exceeding the coercive field, typically above 100 kV/cm, so the EC materials should possess also high dielectric breakdown strength. It has been shown that Mn-doping of lead-based perovskites significantly reduces their dielectric losses and electrical conductivity, so we expect that such materials could withstand high electric fields. We studied the influence of Mn-doping on dielectric and EC properties of PMN-10PT ceramics. The PMN-10PT ceramic samples with addition of MnO₂ (0.5 and 1.0 mol%) were prepared by the mechanochemical synthesis and sintering at 1200 °C for 2 h. The samples were single-phase perovskites with a relative density above 95 % and grain sizes in the 3-5 micron range. The Mn-addition significantly decreases the dielectric permittivity and losses. Furthermore, doped samples exhibit pinched polarization-electric field loops, indicating that Mn acts as an acceptor dopant. However, doping does not importantly influence the EC temperature change at comparable fields. In the contribution we also discuss the effect of Mn-addition on the dielectric breakdown strength of PMN-10PT ceramics.