Electrical conductivity study of CeO2 - doped SrTiO3 ceramics using impedance spectroscopy

The electrical conductivity of nominally cation stoichiometric compositions of CexSr1 − xTiO3 + x (x = 0, 0.02, 0.04, 0.07, 0.10 and 0.15) was investigated using impedance spectroscopy in the temperature range of 300-700 °C in air. The spectroscopic plots (M// vs. log f and Z// vs. log f) were used to analyze the Nyquist plots (Z// vs. Z/). The grain boundaries of all the tested compositions were found to be highly resistive compared to grains. A sharp decline in the activation energy for grain conductivity was observed on CeO2 addition in SrTiO3. No such sudden decrease in the activation energy was observed in the case of the grain boundary. A defect chemistry model was used to describe the conduction mechanisms existing inside the grain and in the grain boundary of CeO2-doped SrTiO3 samples.