Humidity Sensing Enhancement and Structural Evolution of Tungsten Doped Zinc Oxide Nano-Sensors Fabricated Through Co-Precipitation Synthesis

Nano-sensors samples of pure Zinc oxide and tungsten doped ZnO are employed for the study of their humidity sensing performance, morphological and micro-structural details. The nano-powder for sensors of ZnO1 − xWx (x = 0 to 1.75 mol%) are prepared in molar ratios of 0.50 mol%, 1.25 mol%, and 1.75mol% synthesized through co-precipitation technique. The effect of tungsten incorporation in 0.50 mol%, 1.25 mol% and 1.75 mol% on the structural and morphological properties of nanostructures has been investigated via XRD and SEM, respectively. The XRD of the synthesized ZnO nanomaterial possess hexagonal wurtzite structure for all the samples. The obtained diffractogram depicts high and broad peaks implying good crystallinity and smaller crystallite size. The molarity of the dopants yields sufficient reduction in crystallite size from 44.46 nm to 37.38 nm. The crystallite size of the samples calculated using W-H analysis yields 44.28 nm to 39.37 nm. The strain (ϵ) and stress (σ) produced in the crystal due to dopants is analyzed via USDM, UDEDM and SSP thereby deducing energy density ‘u’. The pelletized nano-sensors of diameter 10 mm and thickness 2 mm show excellent response towards humidity sensing within the range of 10–90% of relative humidity. An appreciable sensitivity of 144x and hysteresis of 8.24 is exhibited 1.75 mol% W-ZnO humidity sensor and good stability over a period of 270 days with minimum aging effects.