Physical, Electrical Properties and Gas Sensing Performance of Pure and NiO-Modified ZnO Thick Films

Gas sensing properties of NiO-modified ZnO thick films was studied by dipping the thick films of pure ZnO material prepared by screen printing technique in to 0.01 M aqueous solution of Nickel Chloride (NiCl2) for different interval of time (10, 15 and 20 min). The films were dried at 80 degrees C under IR lamp, followed by firing at 550 degrees C for 1 h in air ambience. The NiCl2 dispersed on the film surface oxidized in firing process converted in to NiO. The morphological properties of the films were investigated by SEM and the final composition of each film was determined by EDAX analysis. The gas response, selectivity, response and recovery time of the thick films were measured and presented. The gas sensing performance of the films was tested for various gases as function of operating temperature. The NiO-modified ZnO film (15 min dipping) was found to be more sensitive to H2S gas (500 ppm) than pure and other modified films (10, 20 min dipping) with fast response and recovery time.