Experimental determination of intrinsic parameters in double-donor-doped(Ba0.92Sr0.08)TiO3-based positive temperature coefficient ceramics

Abstract

In the present work, double-donor-doped(Ba0.92Sr0.08)TiO3-based positive temperature coefficient (PTC) ceramics were fabricated for potentialapplication in an over-current protector. The electrical properties of the materials were alsocharacterized. Using the experimental results obtained, theoretical models onelectrical properties were studied, and the intrinsic parameters were determined. Therelationship between the intrinsic parameters, the materials variables and theelectrical properties was discussed. It was noted that the addition of double donorsY2O3+Nb2O5 could result in relatively low room-temperature resistivity, in particular,30 Ω cm at the sinteringtemperature of 1230 °C. Within the investigated working temperature range, the grain-boundary potential barrierat a fixed measuring temperature decreased with increasing sample sintering temperature.The evaluated effective donor concentration and surface acceptor state density werein good agreement with the reported values in the literature. A parameter wasintroduced based on these two variables to represent the resistivity jump. Thedepletion layer thickness was determined to be in the submicron range. The presentwork is believed to be the first report to determine, based on the experimentaldata, all the essential intrinsic parameters for double-donor-doped PTC ceramics.