Characterization of tin (IV) oxide based semiconductor elements for electronic detection of methane

Tin (IV) oxide based semiconductor devices have been widely applied for the electronic detection of flammable, toxic and polluting gases in ambient air. However, the commercial devices available to date are used qualitatively to monitor CH₄ levels. This study reports a detailed analysis of CH₄ detection using sintered slabs of SnO₂ with Pd as additive. The intention is to investigate the possibility of quantitatively applying the material as the active element in methane-detecting devices. Conductance changes to CH₄ in air (at the ppm levels) are investigated with respect to composition of Pd content (in wt %) in SnO₂ and the effect of flow rate of the carrier gas. It was confirmed that the optimum composition of Pd content in SnO₂ for CH₄ detection is in the range 2-5wt%. The dependence of sensitivity of the elements on CH₄ concentration in the range 50-25,000 ppm was found to be logarithmic and the flow rate of the ambient gas was found to affect the sensitivity, response and recovery times of the sensor elements prepared by sintering at 900°C. Surface morphology of the sintered elements studied by SEM facilitated a theoretical analysis of the mechanism of CH₄ detection using these elements