Selective CO gas detection of SnO2-Zn2SnO4 composite gas sensor

For the selective detection of CO against H-2 gas, SnO2Zn2SnO4 composite-ty pe sensors were fabricated. The surface of the pellet-type composite sensor s was coated by CuO after sintering at 1000 degreesC for 3 h. The electrica l conductivity and the sensitivity of the sensors to reducing gases (200 pp m CO and 200 ppm H-2) were examined by measuring the current-voltage (I-V) characteristics of the composite sensors between 80 and 450 degreesC. The coating of CuO lowered the temperature showing the maximum sensitivity of SnO2 for either CO or H-2 gas. However, the addition of small amount of spinel zinc stannate (Zn2SnO4) into SnO2 provided the sensitivity to CO gas at low temperature (similar to 270 degreesC) while the sensitivity to H-2 gas was maintained at high temperature (similar to 340 degreesC). Further i ncrease of Zn2SnO4 content moved the sensitivity curves to CO and H-2 gases toward high temperature. Thus, the high selectivity for CO gas was obtaine d in the temperature range between 150 and 300 degreesC depending upon Zn2S nO4 content. (C) 2001 Elsevier Science B.V. All rights reserved.