The Effect Of Sio_2 Addition And Measurement Temperature On The High-field Electrical Behavior Of Batio_3-based Positive Temperature Coefficient Thermistors

摘要

The effects of SiO_2 addition, in the range 0-3 at. %, on the high field electrical characteristics of positive temperature coefficient of resistance (PTC) thermistors have been characterized at several temperatures above the ferroelectric transition temperature T_C. It was found that decreases in SiO_2 content and increases in measurement temperature both decreased the field dependency of the current-voltage response. The electrical data were analyzed in terms of existing current-flow models and found to exhibit reasonable agreement only with the model based on diffusion limited transport across a double Schottky barrier. The maximum value of voltage drop per grain boundary for fit to the diffusion limited model V_(max) increased with increasing measurement temperature within the PTC region, but leveled off beyond the temperature of maximum resistance. This behavior directly parallels the variation of electrostatic barrier height with temperature. A reduction in V_(max) with increasing SiO_2 content was observed and attributed to a concomitant reduction in electrostatic barrier height.