Strong effects of gallia on structure and selective responses of Ga2O3–In2O3 nanocomposite sensors to either ethanol, CO or CH4

Abstract

Gallia–In2O3 nanocomposite sensors containing 0–75wt% gallia calcined at 500–850°C are fabricated via co-precipitation method and their response to ethanol, CO, methane and volatile organic compounds is investigated at different operating temperatures. The samples were characterized by X-ray diffraction, energy-dispersive X-ray spectroscopy, high-resolution transmission electron microscopy and BET surface area measurement techniques. Depending on gallia content and calcination temperature, different phases of α- and β-Ga2O3 and c- and rh-In2O3 are formed. The sensors’ responses and selectivities strongly depend on their gallia content and operating and calcination temperatures. At 300°C, 10wt% Ga2O3–In2O3 and 25wt% Ga2O3–In2O3 sensors calcined at 500°C show maximum response to ethanol and CO, respectively, while the maximum response to methane is observed at 400°C by the sensor containing 65wt% Ga2O3. 25wt% Ga2O3–In2O3 calcined at 850°C is selective to methane at 400°C, however, 75wt% Ga2O3–In2O3 calcined at 650°C shows no response to methane. Also, this sensor calcined at 850°C is selective to either CO or methane at 350 and 650°C, respectively, in presence of ethanol and other volatile organic compounds. The sensor containing 65wt% gallia calcined at 500°C is selective to CO in presence of ethanol and methane at 250°C. In addition, the sensor containing 25wt% gallia is selective to VOCs in presence of CO and methane, at the low temperature of 200°C.