EPR and DRS evidence for NO sub(2) sensing in Al-doped ZnO

Zinc oxide (ZnO) is a well-known semiconducting multifunctional material wherein properties right from the morphology to gas sensitivity can be tailor-made by doping or surface modification. Aluminum (Al)-incorporated porous zinc oxide (Al:ZnO) exhibits good response towards NO sub(2) at low-operati...

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Bibliographic Details
Published in:Sensors and actuators. B, Chemical Chemical, 2008-03, Vol.130 (2), p.668-673
Main Authors: Navale, S C, Ravi, V, Srinivas, D, Mulla, I S, Gosavi, S W, Kulkarni, S K
Format: Article
Language:English
Subjects:
Aluminum
Detection
Doping
Interstitials
Nitrogen dioxide
Operating temperature
Signatures
Zinc oxide
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Summary:Zinc oxide (ZnO) is a well-known semiconducting multifunctional material wherein properties right from the morphology to gas sensitivity can be tailor-made by doping or surface modification. Aluminum (Al)-incorporated porous zinc oxide (Al:ZnO) exhibits good response towards NO sub(2) at low-operating temperature. The NO sub(2) gas concentration as low as 20ppm exhibits S=17% for 5wt.% Al-incorporated ZnO. The NO sub(2) response increases with operating temperature and concentration and reaches to its maximum at 300 super(o)C without any interference from other gases such as SO sub(3), HCl, LPG and alcohol. Physico-chemical characterization likes differential thermogravimetric analysis (TG-DTA) electron paramagnetic resonance (EPR) and diffused reflectance spectroscopy (DRS) have been used to understand the sensing behavior for pure and Al-incorporated ZnO. The TG-DTA depicts formation of ZnO phase at 287 super(o)C. The EPR study reveals distinct variation for O super(-) (g=2.003) and Zn interstitial (g=1.98) defect sites in pure and Al:ZnO. The DRS studies elucidate signature of adsorbed NO sub(x) species in aluminium-incorporated zinc oxide indicating its tendency to adsorb these species even at low temperatures. This paper is an attempt to correlate the gas sensing behavior with the physico-chemical studies such as EPR and DRS.
ISSN:0925-4005
DOI:10.1016/j.snb.2007.10.055