Analysis on activation energy and humidity sensing application of nanostructured SnO2-doped ZnO material

Paper reports activation energy and humidity sensing studies of SnO2-doped ZnO nanomaterial prepared by solid-state reaction route. Prepared nanopowders were hydraulic-pressed to form pellets and annealed at temperatures of 400 °C to 700 °C. Pellet samples of SnO2-doped ZnO nanomaterials with 2, 6, 10, 15 and 16 wt% of SnO2 in ZnO were prepared. XRD showed peaks of tetragonal cassiterite and hexagonal zincite. For the best sample of 15% SnO2-doped ZnO nanomaterials, the crystallite sizes were in the range of 27-124 nm evaluated from XRD. Average grain size for this sample as measured from SEM micrograph was 198 nm. SEM micrograph suggested agglomeration of smaller crystallites to form larger grains. Low activation energy value suggested that the sample could be used at room temperature. An increase of SnO2 percentage in ZnO as well as the increase in annealing temperature both enhanced the sensitivity of the sample. Sensing element of 15 wt% SnO2-doped ZnO, annealed at 700 °C, showed the best results with sensitivity of 32.16 MΩ/%RH in the 15%-95% relative humidity range. Properties like low hysteresis, less effect of ageing and high reproducibility were exhibited by this sample.