1Nanomaterials and Sensors Research Laboratory, Department of Physics, Lucknow University, Lucknow 226007, U. P., India
2Department of Applied Physics, School for Physical Sciences, Babasaheb Bhimrao Ambedkar University, Lucknow 226025, U.P., India
Adv. Mater. Lett., 2012, Current Issue, 3 (3), pp 197-203
Publication Date (Web): Jun 10, 2012
Copyright © IAAM-VBRI Press
Present paper deals with a comparative performance of n-type ZnO, ZnO-TiO2 and ZnO-Nb2O5 nanomaterials as humidity sensors. ZnO was synthesized through hydroxide route. TiO2 and then Nb2O5 were used as additives for improvement of sensitivity. Scanning electron micrograph of ZnO shows rod-like particles with average diameter 40 nm. Structural properties by X-Ray diffraction were studied. The minimum crystallite sizes of ZnO-TiO2 and ZnO-Nb2O5 calculated from Scherrer’s formula were found to be 19 and 17 nm respectively. The pellet of each sensing material was annealed at temperatures 150, 300, 450 and 550 ?C for 3 h and checked for its sensing efficiency. Each heat treated pellet was exposed to humidity under controlled condition and variations in resistance with the humidity were recorded. Comparative study of sensitivities of each sensing element was performed. Average sensitivity achieved was 8 MΩ/%RH for the n-type ZnO annealed at 550 ?C. After chemical mixing of TiO2, the sensitivity increased to 18 MΩ/%RH and after Nb2O5, it was found to be 19 MΩ/%RH. Activation energy of electrical transport and Kelvin radii of each sensing elements were also studied.
Humidity, sensitivity, nanostructures, resistance, surface morphology.