Electrical properties of the positive temperature coefficient of resistance (PTCR) ceramics of compositions PbxSr0.994-xY0.006TiO3 (x = 0.5, 0.6 and 0.7) with Curie point over 140°C up to 280°C were studied. The built-in potentials formed at grain boundaries in these ceramics were determined on the basis of the Heywang model. These built-in potentials are found to increase with increasing temperature and contribute to the PTCR effect of the ceramics. The resistances of grain and grain boundary of the ceramics were studied using the complex-plane impedance method. It is clearly observed that the grain resistance of the ceramic is much smaller compared to its grain boundary resistance and the change in resistivity with temperature is contributed mainly by the variation of grain boundary resistance.
- Built-in potentials
- Complex-plane impedance method
- Heywang model
- Positive temperature coefficient of resistance