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Zinc Oxide Varistor Gas Sensors: I, Effect of Bi 2 O 3 Content on the H 2 ‐Sensing Properties

1995; Wiley; Volume: 78; Issue: 9 Linguagem: Inglês

10.1111/j.1151-2916.1995.tb08661.x

1551-2916

Feng‐Gang Lin, Yuji Takao, Yasuhiro Shimizu, Makoto Egashira,

Transition Metal Oxide Nanomaterials

Current ( I )‐voltage ( V ) characteristics of porous ZnO varistors with different Bi 2 O 3 content have been investigated in air as well as in H 2 ‐air mixtures in the temperature range room temperature (RT)‐600°C. The I‐V characteristics measured at RT remained unchanged in the presence of H 2 , but the breakdown voltage clearly shifted to a lower electric field in the temperature range 400–600°C. The breakdown voltage decreased with increasing H 2 concentration in air. The optimum amount of Bi 2 O 3 for the largest decrease was found to be 1.0 mol%. Thus, ZnO varistors can be used as a new type of H 2 sensor. The results presented in this study also suggest the important role of excess oxygen ions existing at the ZnO‐ZnO grain boundaries in developing the Schottky barrier as well as in the H 2 ‐sensing mechanism of the varistors.