Effect of temperature on the electrical properties of (WO3•Co2O3) composite

The composite with the mole ratio of WO3 to Co2O3 being 3:1 was fabricated by the conventional solid-state reaction process. The electrical properties of the sample were measured at various ambient temperatures in a low electric field (E < 200 V/mm). The results demonstrated that the electrical behavior of the composite was sensitive to the variation of the ambient temperature. As the temperature increased, the composite displayed negative differential resistance characteristic within the temperature range of about 50-130 degrees C. When the temperature was between 140 and 300 degrees C the composite exhibited sublinear electrical behavior where current rose more weakly than voltage, which is sharply unlike those in varistors. An obviously superlinear property, exploited in varistors, was observed at the temperature of 500 degrees C. The present results also suggested that the composite did not obey the Arrhenius law. The current-voltage (I-V) properties of the composite could be explained by the double p-n junction and Joule heat. (C) 2011 Elsevier B.V. All rights reserved.