Gas Sensing Properties of Pure and Cr Activated WO3 Thick Film Resistors

Abstract: Thick films of WO₃ (Tungsten Oxide) were prepared by screen-printing techniques. The surfaces of the films were modified by dipping them into an aqueous solution of Chromium Oxide (CrO₃) for different intervals of time, followed by firing at 550 ^oC for 30 min. The gas sensing performance of the pure and Cr₂O₃-modified films was tested for various gases at different temperatures. The unmodified films showed response to H₂S, ethanol and cigar smoke. However Cr₂O_3-modified films suppresses gas sensing response to all gases except H₂S. The surface modification, using dipping process, altered the adsorbate-adsorbent interactions, which gave the specific selectivity and enhanced sensitivity to H₂S gas. The gas response, selectivity, thermal stability and recovery time of the sensor were measured and presented. The role played by surface chromium species to improve gas sensing performance is discussed.

Keywords: WO₃thick film, Cr₂O₃-modified films, H₂S gas sensor, thick films, selectivity, response and recovery time.

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1Materials Research Lab, Department of Physics, K.T.H.M. College, Nashik 422002, India

¹Materials Research Lab, Department of Physics, K.T.H.M. College, Nashik 422002, India