Thermal and Electrical Properties of Tungsten Oxide (WO₃)

Abstract

Thermal and electrical properties of tungsten oxide were observed in a wide range of temperature. An entirely new anomaly was found at 1230°C, where the rate of sublimation increased abruptly. The amounts of anomalous heat were found to be 330, 450, 280 and 120 cal/mol at the 330°C, 740°C, 910°C and 1230°C transitions respectively, the entropy change being 0.55, 0.45, 0.23 and 0.08 cal/mol·deg at each of the transition temperatures. Any anomalous heat larger than 6 cal/mol was not observed near the −20°C transition point. At the mentioned transition points the anomalies of electrical properties were observed. The d.c. resistance decreases, on heating from room temperature, like a typical semiconductor with the activation energies of nearly 2.2, 0.3, 1.7 and 1.3 eV below 740°C, between 740°C and 910°C, between 910°C and 1230°C and above 1230°C, respectively, the small value as 0.3 eV between 740°C and 910°C being especially noticeable. A non-linearly of I-V relation was observed, indicating some anomalous electrical property of this substance.