H_2 Sensing Properties of Metal Oxide Semiconductors as Varistor-Type Gas Sensors
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Current-voltage characteristics of semiconductive oxides have been investigated in air and in H<sub>2</sub> balanced with air at elevated temperatures. A shift in breakdown voltage to a high electric field was observed for Cr<sub>2</sub>O<sub>3</sub>, which is a typical p-type semiconductor, upon exposure to H<sub>2</sub>, while n-type semiconductors exhibited a reverse shift in breakdown voltage. Among oxide specimens, Nb<sub>2</sub>O<sub>5</sub> was found to be the most excellent candidate for a varistor-type sensor, being accompanied with high H<sub>2</sub> sensitivity, excellent mechanical strength and good resistance to high electric field. Further investigations have revealed that the H<sub>2</sub> sensing properties of Nb<sub>2</sub>O5 could be improved by 1.0mol% Bi<sub>2</sub>O<sub>3</sub> doping. Newly formed Bi<sub>2</sub>Nb<sub>10</sub>O<sub>28</sub> phase was suggested to play an important role in enhancing breakdown voltage in air and then the H<sub>2</sub> sensitivity.
- The Journal of the Institute of Electrical Engineers of Japan
The Journal of the Institute of Electrical Engineers of Japan 117(11), 560-564, 1997-11
The Institute of Electrical Engineers of Japan