A high sensitivity gas sensor for formaldehyde based on CdO and In2O3doped nanocrystalline SnO2

The gas-sensing characteristics of In(2)O(3) and CdO doped nanocrystalline SnO(2) compounds for formaldehyde were investigated in this study. The phases of the resulting materials and the morphologies of the sensing layers were characterized by x-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. Indirect-heating sensors using SnO(2)-In(2)O(3)-CdO compounds as sensitive materials were fabricated on an alumina tube with Au electrodes and platinum wires. All measurements were performed at several operating temperatures from 100 to 180 °C. Good gas-sensing responses to formaldehyde have been found for all the prepared samples. It is shown that the sensors exhibited high sensitivity at low operating temperature (133 °C), making them promising candidates for practical detectors for formaldehyde.