Nanaostructured ZnO, ZnO-TiO2 And ZnO-Nb2O5 As Solid State Humidity Sensor

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

DOI: 10.5185/amlett.2012.4330

Publication Date (Web): Jun 10, 2012

Copyright © IAAM-VBRI Press

E-mail: balchandra_yadav@rediffmail.com

Abstract

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.

Keywords

Humidity, sensitivity, nanostructures, resistance, surface morphology.