Effect of MoO3 doping and grain size on SnO2-enhancement of sensitivity and selectivity for CO and H2 gas sensing

MoO3-doped SnO2 nano-particles were prepared using sol-gel method with 0.1 molar solutions of SnCl4-5H(2)O and MoO3 with different doping concentration from 5.03 x 10(-4) to 5.04 x 10(-3) mol. The average grain size varies from 12 to 80 nm obtained by varying calcination temperature from 300 to 900 degreesC. Thick film samples, of about 25 mum thickness, were tested for CO and H-2 in the concentration range of 15-1000 ppm in ambient air. The samples exhibit selective response to CO and H-2 at 140 and 240 degreesC, respectively. The sensitivity increases with doping concentration for H-2, whereas, for CO, it increases rapidly till the doping concentration of 2.01 X 10(-3) mol and then reaches to saturation. The observed maximum sensitivity factor for CO at 2.01 X 10(-3) mol doping is similar to30, whereas for H-2, it is similar to10 at 5.04 x 10(-3) mol doping. The response and recovery time is similar to5 and 10 s respectively. (C) 2002 Published by Elsevier Science B.V.