Studies on gas sensing performance of pure and surface modified Ti02 thick film resistors

Thick films of AR grade TiO₂ were prepared by standard screen- printing technique. The gas sensing performances of thick films were tested for various gases. It showed maximum sensitivity to H₂S at 300°C for 100 ppm. To improve the sensitivity and selectivity of the film towards a particular gas, TiO₂ thick films were surface modified by dipping them in an aqueous solution of 0.01 M nickel acetate tetra hydrate for different intervals of time. These surface modified TiO₂ film showed larger sensitivity to H₂S gas (100 ppm) than pure TiO₂ thick film at 300°C. Nickel oxide on the surface of the films acts as a catalyst and it increases reactivity of the films to H₂S gas. A systematic study of sensing performance of the sensor indicates the key role-played by nickel oxide on the surface. The sensitivity, selectivity, response and recovery time of the sensor were measured and presented.