Electrical characterization of Sr0.97Ti1-xFexO3-delta by complex impedancespectroscopy: I, materials with low iron contents

Impedance spectroscopy has been used to characterize Sr0.97Ti1-xFexO3-delta materials. This technique was suitable to evaluate the grain and grain-bou ndary conductivities of samples with less than or equal to5% iron. The role of grain boundaries was changed by sintering in different conditions, and this was interpreted by accounting for microstructural differences. The cor responding relaxation times were also used to confirm the interpretation of complex impedance spectra. The values of grain-boundary conductivity and t he corresponding values of activation energy obtained by this method were r elatively close to predictions obtained on assuming a p --> n inversion at the grain-boundary core, as proposed by Waser and coauthors.(1-3) The tempe rature dependence of relaxation times confirmed this finding.