LPG sensing properties of platinum doped nanocrystalline SnO2 based thick films with effect of dipping time and sintering temperature

CATEGORY: LPG – LIQUEFIED PETROLEUM GAS
Advanced Materials Letters. Jan2013, Vol. 4 Issue 1, p58-63. 6p. DOI: 10.5185/amlett.2013.icnano.228.
LPG sensing properties of platinum doped nanocrystalline SnO2 based thick films with effect of dipping time and sintering temperature.
A. D. Garje; S. N. Sadakale.
Department of Physics, Sir Parashurambhau College Pune, Pune-411030, India
Abstract
Synthesized nanophase SnO2 powder is used to fabricate thick film resistors using screen printing technology. The surfaces of the thick film resistors were modified by dip coating in platinum chloride (PtCl2) solution of optimized 1.5 M for different time periods of 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10 minutes. Sintering of the films is carried out at different temperatures of 550, 600, 650, 700, 750 and 800°C. The films were tested for 400 ppm of LPG.Thick films which were dip coated for 5 minutes and sintered at 750oC show the highest sensitivity towards LPG which is ten times higher than undoped SnO2 sensors. The characterization of the sensors was done using XRD, EDX and SEM. The sensors were found to be extremely stable and repeatable with a response and recovery time of 10 and 22 s with a minimum detection limit of 5 ppm.
Introduction
Nanocrystalline metal oxide based thick film resistors as gas sensing devices have attracted great attention for a long time due their low cost, ease of fabrication and high sensitivity towards toxic gases. A good chemical and thermal stability under operating conditions along with high mobility of conduction electrons are the important features of the SnO2 based gas sensors. Most of the sensors based on commercially available bulk tin oxide is severely affected by the small surface to volume ratio and also operate at relatively high temperatures of over 573 K. On the other hand nanosized tin oxide have a high surface to volume ratio hence more surface area is available for gas sensing. Low level gas detection via surface modifications of senors is a recent area of thrust. Metal additives such as Pd, Pt are dispersed on the oxide as activators or sensitizers to improve the gas selectivity and to lower the operating temperature. The method used to introduce the additives and the subsequent thermal treatments performed play an important role in distribution of the additives on the surface of SnO2. The additives modify the microstructure of the base material and introduce donor or acceptor levels which cause the variation the resistivity of metal oxide.Dipping a film in chloride solution of noble metals (PtCl2, PdCl2) and then decomposing at or slightly above the decomposition temperature of the additive causes the doping of respective noble metal on the film.In the present work nanocrystalline tin oxide based thick film resistors prepared by screen printing technology and doped with platinum by dip coating in PtCl2 solution for different time periods and sintered at various temperatures for 5 hrs. The effects of dipping time and sintering temperature on LPG sensing properties of SnO2 based thick films have been investigated.
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