Relation between dielectric permittivity and electrocaloric effect under high electric fields in the Pb(Mg_1/3Nb_2/3)O₃-based ceramics

The correlation between dielectric permittivity and electrocaloric (EC) temperature change (ΔT_EC) has been investigated in (1 − x)Pb(Mg_1/3Nb_2/3)O₃−xPbTiO₃ (PMN–100xPT, with x = 0, 0.05, and 0.10) relaxor ferroelectric ceramics. At a given electric field, both peak temperatures, including the temperature of the permittivity peak (T_m) and the temperature of the maximum of the ΔT_EC (T_EC max) increase with increasing PT content. The peak of the dielectric permittivity is, regardless of the applied electric field, always at a higher temperature than is the T_EC max, and the temperature gap between both maxima progressively increases with increasing applied DC bias. This is particularly true above the threshold field, which induces the long-range ordered ferroelectric state. The results, which are explained in terms of the electric field–temperature phase diagram of relaxor systems, thus reveal that T_m can only roughly mark the temperature of the upper boundary of the temperature–electric field window, where the EC responsivity (ΔT_EC/ΔE) is the highest.