Electrical conductivity of Ca1−xSrxTi0.65Fe0.35O3−δ, x = 0, 0.5 and 1, polycrystalline compounds in the 300–500 K range

Abstract

Bulk and grain boundary electrical conductivity of oxygen deficient CaxSr1−xTi0.65Fe0.35O3−δ, x=0, 0.5 and 1.0, polycrystalline specimens were evaluated by impedance spectroscopy measurements in the 5Hz–13MHz frequency range from 300 to 500K. The ceramic powders were synthesized by solid state reaction and by a chemical route, the polymeric precursor technique. The X-ray diffraction of the samples at room temperature shows the following perovskite crystalline structures: cubic for x=0 and orthorhombic for x=0.5 and 1.0. The impedance plots are composed of two semicircles ascribed to grains (bulk) and interfaces (grain boundaries) contributions. The impedance data show that sintered pellets using powders prepared by solid state synthesis present higher intergranular and intragranular resistivity values than pellets prepared by the chemical route. Observations of scanning probe microscopy topographic images of the surfaces of the sintered pellets show evident differences between the grain morphology of the pellets prepared with powders synthesized by the two routes.