Investigations on Electrical Application, Activation Energy and Humidity/gas Sensing Studies of Synthesized Al Doped Zno Nanomaterials

In the present work, sol-gel method is used for obtaining synthesized Al doped ZnO nanocrystalline powders. In the experiments, zinc acetate (Zn(CH3COO)2.2H2O) is used as starting material, methanol as organic solvent and mono ethanol ammine as surfactant. Aluminium sulphate is used for doping Al. All the sols were mixed in appropriate proportions so that there is 8% Al doping in ZnO. Prepared nanopowder was given pellet shape by applying pressure of 260 MPa. Pellets were annealed in air at different temperatures from 300oC to 600oC for 3 hours. Pellet samples made were categorized AZ-8 (8% Al doped in ZnO). The activation energy values for sample AZ-8 from the Arrhenius plot is found to be 0.036 eV for temperature range 60°C to 140°C and 0.016 eV for temperature range 180°C to 200°C. This sensing element shows lower values of activation energies in the two regions indicating that this sensing element has lower operating temperatures and may be used at room temperature as well. A sudden increase in the current has been observed from the V-I characteristics graph of this sensing element. The humidity sensing studies of these samples were also analyzed. The sample AZ-8 annealed at 600oC is showing the best results with sensitivity of 23.60 MΩ/%RH. The crystallite size from XRD for the sensing element AZ-8 is in the 13-38 nm range. The average grain size as measured from SEM micrograph of this sensing element is found to be 95 nm suggesting agglomeration of the crystallites to form larger grains.