EFFECT OF COMPOSITION ON DIELECTRIC AND ELECTRICAL-PROPERTIES OF THE SR1-XLAXTI1-XCOXO3 SYSTEM

Valence compensated perovskite system Sr1-xLaxTi1-xCoxO3 shows dielect ric relaxer behaviour with very high value of dielectric constant in t he composition range 0.20 < x < 0.40. In this paper the effect of comp osition on microstructure and the resulting electrical behaviour is re ported. The composition's with x = 0.25, 0.30, 0.33, 0.35 and 0.37 hav e been synthesized by solid state ceramic method and dielectric measur ements were made in the temperature range of 300-500 K and frequency r ange of 100 Hz to 1 MHz Grain boundaries played an important role in t heir dielectric behaviour. Complex plane impedance and modulus techniq ues were used to separate out the contributions of grain and grain-bou ndaries to the resulting dielectric behaviour. It was observed that th e bulk resistivity as well as the grain boundaries resistance decrease d with increasing x. Furthermore, impedance analysis demonstrated that extremely high value of dielectric constant observed in these materia ls was due to barrier layers formation at grain-grain-boundaries inter faces.