Effect of composition on dielectric and electrical properties of the Sr1-xLaxTi1-xCoxO3 system

Valence compensated perovskite system Sr1-xLaxTi1-xCoxO3 shows dielectric relaxer behaviour with very high value of dielectric constant in the composition range 0.20 < x < 0.40. In this paper the effect of composition on microstructure and the resulting electrical behaviour is reported. The composition's with x = 0.25, 0.30, 0.33, 0.35 and 0.37 have been synthesized by solid state ceramic method and dielectric measurements were made in the temperature range of 300-500 K and frequency range of 100 Hz to 1 MHz Grain boundaries played an important role in their dielectric behaviour. Complex plane impedance and modulus techniques were used to separate out the contributions of grain and grain-boundaries to the resulting dielectric behaviour. It was observed that the bulk resistivity as well as the grain boundaries resistance decreased with increasing x. Furthermore, impedance analysis demonstrated that extremely high value of dielectric constant observed in these materials was due to barrier layers formation at grain-grain-boundaries interfaces.