In this paper, the electrical and gas-sensing properties of calcined tungst
en trioxide semiconductor materials were investigated. X-ray diffraction, s
can electron microscopy and infrared were used to characterize structure an
d performance of WO3 semiconductor material. The average grain size of WO3
was 22 nm after calcination at less than 800 degreesC and 24-26 nm at more
than 900 degreesC for 1 h. The sensors of indirect heating type were fabric
ated. The effects of calcining temperature and operating temperature on ele
ctrical resistance and sensitivity, and sensitivity-gas concentration prope
rties of the WO3-based sensors were investigated. The sensor based on WO3 e
xhibited high sensitivity and good response characteristics to ethanol gas.
The electrical properties of WO3 were analyzed and the sensitive mechanism
was discussed. (C) 2001 Elsevier Science Ltd. All rights reserved.