Talanta 69 (2006) 187–191 Detection of liquid petroleum gas using mixed nanosized tungsten oxide-based thick-film semiconductor sensor G.N. Chaudhari a,∗ , A.M. Bende a , A.B. Bodade a , S.S. Patil a , S.V. Manorama b a Gas Sensor and Thin Films Laboratory, Department of Chemistry, Shri Shivaji Science College, Amravati 444601, Maharashtra, India b Materials Science Laboratory, Indian Institute of Chemical Technology, Hyderabad 500007, Andhra Pradesh, India Received 18 May 2005; received in revised form 20 September 2005; accepted 20 September 2005 Available online 19 October 2005 Abstract The thick-film semiconductor sensor for liquid petroleum gas (LPG) detection was fabricated using a mixed WO 3 -based sensor. We present the characterization of both their structural properties by means of XRD measurements and the electrical characteristics by using gas-sensing properties. The sensing characteristics such as sensitivity, working range, cross-sensitivity and response time were studied by using nanosized WO 3 -based mixed with different metal oxides (SnO 2 , TiO 2 and In 2 O 3 ) and doped with noble metals (Au, Pd and Pt). The WO 3 -based mixed with 5 wt.% In 2 O 3 and 0.5 wt.% Pd showed the higher sensing characteristic at low concentration of LPG sensor at an operating temperature 225 ◦ C. © 2005 Published by Elsevier B.V. Keywords: LPG sensor; WO 3 ; In 2 O 3 ; Sensitivity; Response characteristics 1. Introduction Since the discovery nearly half a century ago that the charge- carrier concentration on the surface of a semiconductor is sen- sitive to the composition of the surrounding atmosphere [1]. Considerable research has been carried out on the development of novel solid-state gas sensors based on semiconducting metal oxides. As a result many such commercial gas sensors have been developed and marketed [2–4]. The currently acceptable levels of performance are used increasingly to monitor gases in various fields such as industrial and environmental control [5,6]. Different hydrocarbons are widely used for several indus- trial and domestic applications. These gases are potentially hazardous because they can cause explosions if they leak out accidentally or by mistake. Hence there is a great deal of world- wide interest in developing reliable and efficient hydrocarbon sensors having good sensitivity and selectivity. For the last three decades, wide-gap semiconducting oxides such as SnO 2 and ZnO have been extensively studied for making ∗ Corresponding author. E-mail addresses: gnc4@indiatimes.com, gnchau@rediffmail.com (G.N. Chaudhari). efficient hydrocarbon sensors with suitable noble metal additives such as palladium [7,8] and platinum [9,10]. Other well-known materials for fabricating hydrocarbon sensors include WO 3 [9], CO-doped Fe 2 O 3 [11] and In 2 O 3 –Al 2 O 3 doped with Pd [12]. However, the above-mentioned materials are still not as selec- tive as one would expect, since they sense several other reducing gases such as liquid petroleum gas (LPG), H 2 , CO and CH 4 with good sensitivity values. In addition, the stability of some of these materials is not very good resulting in poor reliabil- ity due to aging and humidity-induced effects, involving grain growth and poisoning. These are manifested as a change in resistance over several weeks and hence are not suitable, since they do not offer the good combination of high sensitivity, selectivity and rapid response time reliably required for several applications. Recently, Wang et al. [13] developed a thick-film gas sensor to detect LPG and hydrogen gas based on -Fe 2 O 3 . Further studies and developments of WO 3 -based gas sensors have been accom- plished by Barrett et al. [14], Miura et al. [15] and Akiyama et al. [16]. Barrett et al. prepared WO 3 -based gas sensors of the metal oxide semiconductor (MOS) type by decomposing ammonium tungsten. It was found that the WO 3 -based gas sen- sor was sensitive to H 2 S even at concentrations down to 50 ppm. At the same time, Miura et al. [15] developed a pair of Pt- loaded oxide electrodes as a proton-conductor gas sensor. It was 0039-9140/$ – see front matter © 2005 Published by Elsevier B.V. doi:10.1016/j.talanta.2005.09.024