Effect of single wall carbon nanotube additive on electrical conductivity and methane sensitivity of SnO2

The effect of single wall carbon nanotube (SWCNT) additive on electrical conductivity and methane sensitivity of SnO2 gas sensor has been investigated. Sensors were prepared through powder pressing procedure and the morphology and microstructure of the materials were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques. The electrical resistivity and methane sensitivity of the samples were examined in the temperature interval of 100 to 450 degrees C. Results show that in the air ambient the electrical resistivity of the samples increases with the increase of SWCNT concentration. Also, comparative results show that by increasing of SWCNT concentration up to 1.2 wt%, the methane sensitivity of the samples increases, and after that by further increase of SWNT concentration the sensitivity decreases. Based on the SEM images of the sensors, and also the measurement results, three types of resistance, related to metal oxide, SWCNT bundle, and SWCNT/SnO2 grain junction, were realized in the sensors and based on that, a simple electrical circuit model is proposed. Results show that SWCNT/SnO2 grain junction resistance is the main reason for the higher electrical resistivity of the samples with higher SWCNT concentrations. (C) 2014 Elsevier B.V. All rights reserved.