Preparation, characterization and gas-sensing properties of SnO2–In2O3 nanocomposite oxides

This paper aims at preparing gas-sensing nanocomposites of SnO2–In2O3 using a chemically controlled co-precipitation method and testing their sensing properties for detection of toxic gases. Through manipulating the Sn/In cation ratio, metal salt total concentration, precipitation pH value and aging conditions, the nanocrystalline composite powder was successfully derived with chemical homogeneity and superior thermal stability compared to the single-component oxides. The experimental results showed that these nanocomposites exhibited high sensitivity and selectivity for the detection of CO and NOx, and the sensitivity depended on the composition of the composites, calcination temperature and operating temperature. Their sensing performance was further enhanced through the introduction of a small amount of metals or other oxides as dopants and surface coatings. The gas-sensing mechanism of the nanocomposites was also discussed by X-ray photoelectron spectroscopic (XPS) analysis and temperature-programmed desorption (TPD) studies at gas-sensing operating temperatures.