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

作者：Luthra Vandna; Pratt Keith F E; Palgrave Robert G; Williams David E; Tandon R P; Parkin Ivan P^*

来源：Polyhedron, 2010, 29(4): 1225-1230.

DOI：10.1016/j.poly.2009.12.028

• Oxides
• Chemical synthesis
• Sintering
• Chemisorption
• Electrical conductivity

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.

• 出版日期2010-3-10