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Gas-sensing properties of Fe2-xTixO3+gamma (x=0-1.4)

Luthra, V; Pratt, KFE; Palgrave, RG; Williams, DE; Tandon, RP; Parkin, IP; (2010) Gas-sensing properties of Fe2-xTixO3+gamma (x=0-1.4). POLYHEDRON , 29 (4) 1225 - 1230. 10.1016/j.poly.2009.12.028.

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Abstract

As part of a systematic study of mechanisms of response of semiconducting oxides as trace gas sensors, we have explored the behaviour of iron-titanium oxide solid solutions Fe2-xTixO3 (x = 0.1-1.4). The materials were single-phase for x = 0.1 with increasing proportions of a pseudobrookite second phase at higher degree of substitution. Unmodified, pure iron oxide does not show sensitivity to CO. A significant signal was developed for x = 0.1, that then diminished with increasing x and was lost for x = 1.4. Three effects have been deduced important for the gas response: significant surface segregation of Ti at low Ti content; grain growth inhibition and agglomeration into more massive, non-porous lumps as Ti content increased; and the appearance of a band-gap state associated with Fe(II) at higher Ti content. The effects of microstructure change have been analyzed by fitting the data to a simple 2-resistor model of gas-insensitive 'grains' in series with gas-sensitive 'grain boundaries'. A Mars-van Krevelen type model for the response is presented, based on reactions at surface-segregated defect clusters, to develop and remove electrically-active surface trap states. (C) 2010 Elsevier Ltd. All rights reserved.

Type:Article
Title:Gas-sensing properties of Fe2-xTixO3+gamma (x=0-1.4)
DOI:10.1016/j.poly.2009.12.028
Keywords:Oxides, Chemical synthesis, Sintering, Chemisorption, Electrical conductivity, SENSITIVE RESISTORS, SEMICONDUCTING OXIDES, SURFACE-CHEMISTRY, SENSOR BEHAVIOR, 0-LESS-THAN-X-LESS-THAN-1, ALPHA-FE2O3, MODEL, CTO, SN, TI
UCL classification:UCL > School of BEAMS > Faculty of Maths and Physical Sciences > Chemistry

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