Effect of noble metals on selective detection of liquid petroleum gas by SnO 2
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Effect of noble metals on selective detection of liquid petroleum gas by SnO2 A. R. Phani and M. Pelino Department of Chemistry and Materials, University of L’Aquila, 67040 L’Aquila, Italy (Received 26 February 1997; accepted 28 July 1997)
The present investigation deals with the electrical response of doped SnO2 to improve the selectivity for liquid petroleum gas (LPG) in the presence of CO and CH4 , by utilizing noble metal sensitizers such as Pd, Pt, and Rh. SnO2 with the addition of Pd (1.5 wt. %) or Pt (1.5 wt. %) sintered at 800 ±C which have shown high sensitivity toward LPG with no cross interference of CO and CH4 at an operating temperature of 350 ±C. The results suggest the possibility of utilizing the sensor for the detection of this hydrocarbon gaseous mixture. X-ray diffraction studies have been carried out to evaluate the crystallite size as a function of sintering temperature; x-ray photoelectron spectroscopy studies have been carried out to define the possible chemical species involved in the gas-solid interaction and the sensitivity enhancing mechanism of the SnO2yPd sensor element toward LPG. I. INTRODUCTION
Hydrocarbon gases have been widely used as fuel for domestic purposes and in industry as a clean source of energy. However, they are potentially hazardous because of the high possibility of explosion accidents caused by leakage or by mistake. This has resulted in an increased demand in developing sensors to detect these hydrocarbon gases. The term liquid petroleum gas (LPG) is applied to those hydrocarbons in which the chief component consists of butane (70–80%), propane (5–10%), and propylene, butylene, ethylene, methane (1–5%). To meet the high standards for the detection and sensing of low levels of gases, the sensors should be highly upgraded in terms of sensitivity, selectivity, reproducibility, and stability. Little work has been done on LPG sensors. Seiyama et al.1 reported that the inflammable gases in air could be detected from a change in the electrical resistance of tin film of a ZnO, while Taguchi2 claimed that a porous sintered block of SnO2 could also work in the same way. Several investigators have worked on butane (which is the major component of liquid petroleum) gas sensors using semiconducting oxides as base materials. SnO2 –TiO2 complex oxides doped with Pt as a catalyst and Sb as a conductive dopant were prepared by a co-precipitation method; a sensor element was produced by screen printing technique with enhanced sensitivities to hydrocarbon gases when the loading rate of TiO2 was 3–5 mol %.3 Fe2 O3 , without and with Pd doping, prepared by screen printing, was tested for butane gas and no interfering gases were mentioned.4 V2 O5 supported on ZrO2 has been tested for hydrocarbon gases and found to be sensitive to the mixture of n-butane and propane.5 In the present investigation, which was presented at the Materials Research Society meeting in Boston 1780
http://journals.cambridge.org
J. Mater. Res., Vol. 13, No. 7, Jul 199
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