Nanostructured ZrO<sub>2</sub> Thin Films Deposited by Spray Pyrolysis Techniques for Ammonia Gas Sensing Application

Abstract

The spray pyrolysis deposition technique has number of advantages to produce advance nanostructured oxide films. The film surface morphology and structure depends on the precursor and doping solution and solvents used with their optimized parameters. The surface to volume ratio is achieved is beneficial to gas sensing. Therefore in this paper we report the nanostructured ZrO2 thin films was prepared using spray pyrolysis technique for ammonia gas sensing. There is various precursors such as Zirconium acetylacetonate, Zirconium nitrate, Zirconium tetra chloride etc. In spite of them, the Zirconium oxychloride octohydrate (0.05 M) was chosen as precursor solution and was prepared by dissolving in pure distilled water (Solvent). The films were deposited on heated glass substrate at 350◦C and were annealed at 500◦C for 1 hrs. It was characterized using XRD, FESEM, and TEM technique to examine crystal structure, surface morphology and microstructure properties. The average crystallite and grain size observed to be nanostructured in nature. The different test target gas performances were tested with various concentrations at different operating temperature. The films sprayed for 20 min with optimized spray parameter were observed to be most sensitive (S=58.5) to NH3 for 500 ppm at 150°C. The film thickness dependence parameters: FWHM (0.02678 radians) for peak 111, Inter-planer distance (d=0.2958 nm), lattice parameters Inter-atomic spacing ( a=0.511 nm), atomic volume(a3= 133Å3 ),micro strain (2.8 to 0.76 x 10-2), crystallite size (4-5nm) average grain size (32nm), dislocation density (1.73 x1015 lines/cm2), texture coefficient (>1), specific surface area(31 m2/g), activation energy and band gap were studied. The sensor shows quick response (4 s) and fast recovery (10 s). Reported results are discussed and interpreted