Regular Article

Palladium enriched tungsten oxide thin films: an efficient gas sensor for hazardous gases

¹ Department of Physics, Abasaheb Garware College, Karve Road, Pune 411 004, Maharashtra, India
² Department of Physics, Savitribai Phule Pune University, Ganeshkhind, Pune 411 007, Maharashtra, India

^a e-mail: smb.agc@gmail.com

Received: 25 October 2018
Received in final form: 24 December 2018
Published online: 8 April 2019

Abstract

Palladium enriched tungsten trioxide thin films were prepared by spraying solution of ammonium tungstate as a precursor on glass substrates using spray pyrolysis deposition technique. Palladium chloride as a precursor for palladium was introduced in the precursor solution during refluxing process before deposition. The catalyst Pd with different concentrations was introduced on series of WO₃ films. X-ray diffractometry (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy were applied to analyze structure and morphology of the deposited thin films. The effect of Pd enrichment on the microstructure, electrical and gas sensing properties of the as-synthesized WO₃ thin films was studied. Variation in the electrical conductivity of pure and Pd supplemented WO₃ films was measured in air and in the presence of hazardous gases such as NO₂, SO₂ and NH₃. The addition of 3 w/o Pd in WO₃ raised the gas response of the film to 1.1 towards NO₂ at lowest operating temperature of 100 °C. The film shows adequate response towards SO₂ (0.32) and NH₃ (0.27) at 200 °C and 225 °C, respectively. The response and recovery time ranged in 0.5–1.25 s and 1–6.7 s respectively even for high gas concentrations upto 750 ppm.