Effect of dopants on the properties of tin oxide-based gas sensors

Tin oxide based thick-film gas sensors were fabricated using screen-printing methodology and their gas sensing abilities investigated with respect to their sensitivity to CO. These sensors exhibit a lowering of electrical resistance when exposed to a reducing gas environment e.g., CO, CH4, H-2 C3H8, etc. Various other factors such as temperature, moisture, dopants, gas concentrations, also influence the response and sensitivity of gas sensors. Preliminary results show that the SnO2 sensors exhibit sensitivity to CO at a low concentration of 100 ppm, which is reduced on exposure to moisture. However, the gas sensing abilities are considerably promoted using SnO2 in combination with both Co3O4 as well as a commercial borosilicate glass in the presence of moisture. These properties make them attractive for the detection of CO in the gases emitted during combustion processes, where a higher concentration of water vapors is present in the exhaust gases.