Studies on Ni-SnO2 Nanocomposites for Humidity Sensing Application

We report a hydrothermal method for synthesis of nickel-doped tin oxide (Ni-SnO2) nanoparticles. The samples are characterized by different analysis techniques to understand their structural, morphological, and optical properties. The synthesized nanomaterials are characterized by X-ray diffraction, it is crystallized in a tetragonal rutile crystal structure and the crystallite size increases from similar to 5 to similar to 23 nm with the increasing nickel (Ni) doping concentration. The field emission electron microscopy demonstrates that in case of doping the addition of polyethylene glycol is responsible for the development of densely packed flower like bunches. Further, the synthesized n-type SnO2 materials are systematically investigated for humidity sensing toward atmospheric moisture. The results indicate that nickel doping improves the performance of SnO2 sensor and is highly sensitive over a wide relative humidity (%RH) range from 10% to 100% at room temperature than pure SnO2. It is found that the resistance of the films decreases with increasing RH as the multilayer stacking of water molecules occurred on the surface of synthesized nanomaterials. Also, the fast response time of 15 s and recovery time of 4 s are observed for the 5% nickel-doped SnO2 sensor. This improved sensing performance is attributed to nickel doping as doping developed the proportions of oxygen vacancy and improves the large surface to volume ratio as well as exhibited high conductivity. Thus, the doping of SnO2 nanoparticles with Ni should be a promising approach for designing and fabricating the high-performance humidity sensor.