Current-voltage characteristics and selective CO detection of Zn2SnO4 and ZnO/Zn2SnO4, SnO2/Zn2SnO4 layered-type sensors

The current-voltage characteristics and the CO gas-sensing properties of porous Zn2SnO4 were examined. ZnO/Zn2SnO4 and SnO2/Zn2SnO4 layered-type samples were also fabricated for the investigation of the interfacial effect between ZnO (or SnO2) and Zn2SnO4 by sequentially die-pressing respective powders. To form a stable contact between ZnO (or SnO2) and Zn2SnO4, the composition and thus the sinterability of ZnO (or SnO2) was controlled. The electrical and gas-sensing properties of the layered samples were compared with those of individual ZnO, SnO2 and Zn2SnO4. Zn2SnO4 showed the higher sensitivity values to CO gas than to H-2 gas at relatively low temperature. The sensitivity of Zn2SnO4 decreased with the increasing magnitude of applied voltage at high temperature. Both SnO2/Zn2SnO4 and ZnO/Zn2SnO4, layered-type samples showed the sensing characteristics varying with the direction of applied bias. The interface between Pt and Zn2SnO4 was responsible for the observed non-ohmic current-voltage characteristics and the resultant gas sensitivity. (C) 2001 Elsevier Science B.V. All rights reserved.