Extrinsic contributions to the grain size dependence of relaxor ferroelectric Pb(Mg_1/3Nb_2/3)O₃: PbTiO₃ ceramics

This paper addresses the observed grain size with dependence of the dielectric behavior for Pb(Mg_1/3Nb_2/3)O₃: PbTiO₃ ceramics grain sizes ≥ 1.0 μm. A combined transmission electron microscopy (TEM) analysis and dielectric characterization are modeled with a modified brick wall approach. From this model, it is possible to extrapolate information such as single crystal values of dielectric maximum, K_max, the diffuseness coefficient, δ, and the average intergranular thickness for relaxor ceramics. The calculated intergranular thickness agrees well with TEM observations, ≍2.0 nm. This semi-empirical method may be potentially useful in development work of relaxor ceramics to predict the optimized dielectric properties obtainable within microstructural restrictions.