Conduction—concentration relationship in chemoresistive thick-film SnO 2 gas sensors

Abstract

The steady-state conductance G of thick-film SnO 2 chemoresistive gas sensor is measured for different CO concentrations c in air, in the 0–300 ppm range, at 0 and 100% relative humidity. The conductances G 0 at 0 and G at 120 ppm CO in normal air are measured as a function of time in non-steady-state conditions, during the first two hours of stabilization, after keeping the sensors unheated (out of operation) for seven days. The time dependence of the conductance at sudden changes of the CO concentration between c=0 and c ≠ 0 in normal air is also measured. Experimental results indicate that the ratio ( G 2− G 0 2)/ G 0 depends almost linearly on c down to very low values (about 1 ppm); it is fairly independent of humidity in the steady state, and of time during the stabilization stage. This can offer a possibility for using SnO 2 sensors not only for the detection, but also for the quantitative measurement, of small concentrations of a combustible gas in air.