Propane gas sensing properties of SnO₂ and SnO₂:Ag thin films prepared by sol-gel technique

Both SnO₂ and SnO₂:Ag thin films were fabricated by the sol-gel process and dip-coating technique. SnCl₄·5H ₂O was used as a precursor of tin to prepare a 0.2M solution with 2-methoxyethanol and monoethanolamine as solvents. From AgNO₃ a 0.012M solution in ethanol was prepared, from where the Ag was used as catalyst, which was incorporated superficially to SnO₂ film grown on soda-lime substrate. Two series of samples (A and B) about 150 and 300 nm in thickness were prepared and studied. Several layers of Ag as catalyst on the surface of SnO₂ films were applied. The films were characterized in structure (RXD), morphology (SEM and AFM) and EDX, electrical and optical properties (UV-vis). The sensing properties of films to the propane at, 0, 1, 5, 50, 100, 200, 300, 400 and 500 ppm gas concentrations were tested in sensors operating at 23, 100, 200 and 300°C. Results for a selection of sensors are presented in this paper.