Synthesis, characterization, and gas-sensing property for HCHO of Ag-doped In2O3 nanocrystalline powders

Pure and Ag-doped In2O3 nanocrystalline powders with different doping concentrations have been prepared by a sol–gel method, and characterized by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), and X-ray photoelectron spectrum (XPS). The results indicated that these powders had a good crystalline structure with an average crystallite size of 12 nm. The indirect heating structure sensors were fabricated by loading these powders on ceramic tubes with Au electrodes. Gas-sensing measurements indicated that the sensor fabricated from 8 wt.% Ag-doped In2O3 could detect HCHO gas down to 2 ppm with a short response time (10–15 s) and an excellent selectivity at 100 °C.