Impurity induced dielectric relaxor behavior in Zn doped LaFeO3

Abstract

Sol–gel derived nanocrystalline samples of LaFe1−xZnxO3 have been investigated for their dielectric properties in the broad frequency and temperature range. The pristine sample exhibits an anomaly around Neel temperature in the variation of dielectric permittivity against temperature. However, the loss factor shows frequency dependent peak indicating the relaxational behavior in the LaFeO3 system. The incorporation of Zn enhances the relaxational behavior in the pristine system. A.C. conductivity is determined for all the samples in the temperature range 300–600 K. Activation energy determined in the high-temperature range (500–600 K) may correspond to the motion of singly ionized oxygen vacancies, in the vicinity of 450–500 K corresponds to the motion of doubly ionized oxygen vacancies within the single FeO6 octahedra and in the lower temperature range (300–450 K) it may correspond to hopping of electrons between Fe2+ and Fe3+ ions. The hopping conduction mechanism has been investigated from the temperature dependence of the “s” parameter. The conduction mechanism in pristine sample is governed by the correlated barrier hopping (CBH) model. However, in doped samples, the conduction mechanism follows both CBH and non-overlapping small polaron tunneling (NSPT) models.