Complex Impedance Analysis for Sensitivity and Selectivity of SnO_2 Gas Sensors

The impedance characteristics of thick films gas sensors were investigated by measuring the dependence of the reactance component on frequency in testing gas. Using the variations of reactance with the concentration of gasoline or alcohol gas to define the sensitivity of gas sensors,a new method greatly improving the sensitivity and selectivity of gas sensors compared with the traditional d.c. method was proposed. Such improvements maybe come from that the complex impedance analysis detects not only the change of grain boundary resistance but also the change of grain boundary caparitance with the gas adsorption and/or desorption on the surfaces of sensors.