Preparation, Characterization And Performance Of La Doped Sn02 Catalytic Pellet For Detection Of Volatile Organic Compounds
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Date
2010-10
Authors
Ang, Gaik Tin
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Abstract
Sn02 catalytic pellets doped with 0-10 atomic % lanthanum were developed
by sol gel method and characterized by X-ray diffraction (XRD), transmission
electron microscope (TEM), surface analysis (Nitrogen adsorption-desorption) and
scanning electron microscope (SEM). Prior the gas sensor measurement, Lab VIEW
software was programmed to interface with the electrometer to get all measured
electrical resistance values. The electrical resistance change of the catalytic pellets
was investigate~ using volatile organic compound (VOC) vapours i.e. ethanol,
acetone and methanol in the air at the temperatures between 150-350°C.
The sensitivity of the Sn02 catalytic pellet was greatly enhanced by the
addition of lanthanum. The sensitivity of 5.0 atomic% La doped in Sn02 was up to
50.52 for 500ppm ethanol at working temperature of 250°C, while that of pure Sn02
is 14.84. The improvement in sensitivity may be attributed to the formation of small
Sn02 crystallite size, high surface area and the presence of the basic sites, which
facilitated the dehydrogenation process. Increasing of La content in the catalytic
pellet up to 7.5 atomic% deteriorated the ethanol sensitivity. Additionally the dopant
La in Sn02 sensors showed good selectivity to ethanol over methanol and acetone.
The 5.0 atomic% La-doped Sn02 exhibited very short response time of 14 seconds
with the high sensitivity value of 29.9 for the detection of 100 ppm of ethanol. The
linear dependence of the sensitivity on the ethanol concentration is observed in the
range of 100-1500 ppm. The gas sensor exhibited high repeatability, reliable
sensitivity after repeated use for 12 days. Our results demonstrated that the dopant La
in Sn02 was promising in fabricated VOC sensors which could work at a low
temperature.
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Keywords
Preparation, characterization and performance of La doped sn02 catalytic pellet for detection , of volatile Organic compounds.