Describing the effect of Ag/Au modification on operating temperature and gas sensing properties of thick film SnO2 gas sensors by gas diffusion theory

The effect of Ag and Au additives on the optimum operating temperature and response level of thick film SnO2 gas sensors is investigated and compared with the results of pure SnO2 ones. Fabricated samples were examined at various atmospheric conditions and at different operating temperatures (130–400 °C). It is shown that compared with pure SnO2 samples, in Ag-SnO2 samples 50 °C reduction of operating temperature and 7 times increase of response level is achieved. The achieved modifications are 70 °C reductions in operating temperature and 4 times increase of response level for Au-SnO2 samples. In addition to reporting the improving properties of SnO2 samples by adding Ag and Au, the validity of the gas diffusion model was also verified in these metal added samples for the first time. Gas diffusion theory is a comprehensive theory which its validity in resistive gas sensors has been verified by many researchers. The parameters of gas diffusion model were extracted for all fabricated sensors to achieve better understanding of their sensing properties. •The validity of gas diffusion theory in metal added SnO2 gas sensors was proved for the first time.•Gas sensing mechanism of samples has been described by considering the diffusion theory.•The effect of Ag and Au on the optimum operating temperature of SnO2 sensors is investigated.•It is shown that in resistive gas sensors the optimum operating temperature is independent of gas concentration.