Polaronic relaxation in perovskites

We report a low-temperature loss anomaly in several oxidic perovskites such as ${\mathrm{KTaO}}_3$, ${\mathrm{KTaO}}_3$:Nb, ${\mathrm{SrTiO}}_3$, ${\mathrm{SrTiO}}_3$:Ca, ${\mathrm{PbTiO}}_3$:La, Cu, and ${\mathrm{BaTiO}}_3$:La. We show that this anomaly arises from a low-frequency dielectric relaxation. The activation energy and the relaxation time of this process are nearly the same for all the investigated perovskites disregarding their composition, texture, and ferroelectric properties. We thus ascribe the loss anomaly to the localization of polarons on residual defects. Although the dielectric losses in ${\mathrm{SrTiO}}_3$ and ${\mathrm{SrTiO}}_3$:Ca are qualitatively similar to other perovskites, the loss anomaly occurs at much lower temperatures: 10 instead of 40 K.