Spray pyrolyzed indium oxide thick films as NO2 gas sensor

Abstract Metal oxides are proven as efficient materials in the detection of various toxic gases at moderately high temperature. In this study, efforts are made to deposit indium oxide (In 2 O 3 ) thick films by using a simple spray pyrolysis method. The In 2 O 3 films were deposited at different concentrations of spray solution at 400 °C. The solution concentration was varied over 0.03–0.1 M. The structural and morphological properties of In 2 O 3 films were studied using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The cubic crystal structure of synthesized In 2 O 3 films was confirmed by XRD patterns. The crystallite size increases with the increase in the solution concentration. The surface morphology was substantially changed with solution concentration and revealed increase in average grain size. The nanopetal like morphology was obtained at 0.07 M spray solution concentration. The deposited In 2 O 3 films were employed for gas sensing applications. The In 2 O 3 films deposited at 0.07 M solution concentration showed maximum sensor response (R g /R a )~33.45 at 150 °C for 100 ppm of NO 2 gas.