Effect of silver additive on electrical conductivity and methane sensitivity of SnO2

A composite powder of tin oxide (SnO2) and silver (Ag) clusters was prepared by a simple and cost effective method of reducing their aqueous mixture with sodium borohydride (NaBH4). Gas sensors based on the composite were made by powder pressing procedure and characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The electrical conductivity and gas sensing behavior of the sensors for methane (CH4) gas were studied as a function of Ag concentration (0.3, 0.5, 0.8 and 1.5 wt%). The Ag additive is found to improve sensor response and widen its working temperature range with notable sensor response. The best sensor response was achieved by the sensor with 0.5 wt% Ag. The enhanced response was proved to be due to both electrical and chemical mechanisms.