Gas Sensing Characteristics of WO3 (I)
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- Category: Tungsten Information
- Published on Thursday, 05 February 2015 17:52
Electrical properties of oxides semiconductor depend on the composition of the surrounding gas atmosphere. The following is the latest progress on gas sensing characteristics of WO3 with three aspects of oxidizing inorganic gases NO2, reducing inorganic gases H2S and organic vapors.
(1) Gas sensing characteristics to NO2
To our best knowledge, much effort on gas sensing characteristics of WO3 prepared by hydrothermal method is devoted to highly toxic NO2. The detection of NO2 is usually based on the formation of absorbed surface-trap states NO2-ads. The resistance of WO3 was increased with the increasing barrier in the conduction band (CB). The resistance increased with the increasing concentration of NO2 because of capturing more electrons from the CB.
It is well known that the gas sensitivity of the WO3 sensing materials to NO2 is much dependent on the annealing temperatures, the additives, the operating temperatures, as well as electrode materials. For example, WO3 nanopowders annealed at high temperature showed better response to NO2 in dry air. This was attributed to the improvement of crystalline quality at higher temperature.
Improving the crystalline quality, reducing the size of product, adding optimal active catalyst and dopant amount as well as optimizing the design of electrode are all good for the gas sensing characteristics of WO3. However, the working temperature is commonly above the room temperature. Even the sensor shows response, the sensitivity value is still low. This drawback limited application of WO3-based gas sensors in a certain extent.
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