Nitrogen Dioxide Gas Sensing Properties of Nanocrystalline In2O3 Thick Films for Environmental Protection

The Sol–gel method was utilised to synthesise the nanocrystalline In2O3 powder with a cubic structure in the current study. Thick film samples of In2O3 powder were prepared on an alumina substrate. A low-cost and straightforward screen-printing method was used for making the film samples. The prepared samples were subjugated to firing at different temperatures in a range of 700 to 850 °C with 50 °C increment. This temperature range assured much better adhesion of films on the alumina substrate. The X-ray diffraction (XRD) study revealed the cubic phase along (222) orientation. The electrical characterization study confirmed the n-type semiconducting nature of the film samples. The film samples fired at 700 °C showed a relatively low resistivity compared to those fired at different temperatures. The particle size was found small with an enormous surface area. The morphology study using scanning electron microscopy (SEM) showed that the particle size also increased as the firing temperature was increased. Film samples fired at 700 °C were also exhibited higher sensitivity and selectivity for nitrogen dioxide gas of 100 ppm concentration at 100 °C operating temperature.