Electrical characteristics of (Pb,Sr)TiO3 positive temperature coefficient ceramics

Abstract

Electrical properties of the positive temperature coefficient of resistance (PTCR) ceramics of compositions Pb,Sr0.0094-xY0.006TiO3 (x=0.5, 0.6 and 0.7) with Curie point over 140 degrees C up to 280 degrees 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 an 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. (C) 1998 Elsevier Science S.A. All rights reserved.