In this work, the nano indium oxide (In2O3) powder is prepared by hydrothermal technique. The prepared powders at different mole (0.1M, 0.2M & 0.3M) were annealed at 350º, 400º and 450º C temperatures respectively. The nanopowder was optimized at 0.2 M with 400º C by XRD investigation. The XRD peak with maximum intensity at (222) plane showed the lattice; bodycentered-cubic (bcc). The gas sensing functions of In2O3 for O3 were tested in terms of electrical conductivity and the efficiency of present sensor in terms of response and recovery rates are very high when compared to commercial detector. The calculated particle size was in the range of 10-20 nm and the particle size was found to be almost uniform and also surface of the crystal was observed regular, which were confirmed by SEM and TEM images. The peaks of In and O in EDAX spectrum ensured the material was free from contamination. The Photoluminescence analysis proved the optical transparency of the prepared material and it is to be the main root cause of radiative centre was oxygen vacancies produced as common defects.
