Effect of oxygen vacancies on SrTiO electrical properties

SrTiO3-δ (δ = 0.075, 0.125 and 0.25) were prepared in two steps: the preparation of the parent compound SrTiO3 by the solid state reaction method followed by the creation of oxygen vacancies δ, through a thermally activated process. X-ray diffraction analysis shows that all samples crystallize in the cubic structure with Pm3m space group. The grain's size distribution and the samples' surface characteristics were assessed by scanning electron microscopy. Impedance spectroscopy was used to characterize the ac electrical properties of these materials as a function of frequency at various temperatures (240–340 K). The impedance data was well fitted to an (R1CPE1)//(R2CPE2) equivalent electrical circuit model. It was found that the electrical behavior of the ceramics is dominated by the grain-boundary response and increased conductivity values were found for a large amount of oxygen vacancy. The frequency dependence of the conductivity was investigated through the Jonscher's universal power law and the electrical conduction mechanism was found to be strongly dependent on the oxygen vacancies concentration.