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Non-homogeneous nanocrystalline oxide materials for gas sensor applications
|Marina N. Rumyantseva , Alexander M. Gaskov
Chemistry Department, Moscow State University, Leninskie Gory, 1-3, Moscow 119992, Russian Federation
The heterogeneous nanometer-scaled oxide materials M1O-M2O (nanocomposites) has pronounced advantages for solid state gas sensor applications. The electronic properties of grain boundaries in two-phase systems are very sensitive to the atmosphere composition. The solid-gas interaction in such systems involves selective chemical reactions on the M1O-M2O grain boundaries. If M2 is a transition metal, the solid-gas interaction may change its oxidation state and distribution between the surface and lattice positions. The behaviour of SnO2-M2O nanocomposites (M2O = Fe2O3, NiO, CuO, PdO, PtO2, RuO2) in relation with gas sensing phenomena has been analysed. The work includes the methods of SnO2 thin and thick films elaboration, investigation of microstructure, surface state and electrical behaviour of nanocomposites in different atmospheres. The mechanism of solid-gas (CO, H2, CH4, C2H5OH, H2S, NO2) interaction is discussed on the basis of results of Mössbauer and Raman spectroscopy, AES, XPS, XAS and conductance measurements. The main information was obtained by in situ techniques. Depending on the ionic radius and charge the M2 elements are variously distributed between the bulk and surface of nanometer-scaled SnO2 grains. In air all regarded elements being distributed in SnO2 matrix are in oxidised state. The common points for all nanocomposites studied are: (i) in nanocoposites the SnO2 grain size is reduced, that can be caused by M2O segregation on SnO2 grain surface leading to kinetic limitations of recrystallisation processes; (ii) M2O affect the SnO2 electrical properties, however the mechanism of resistance growth may be different: the compensation effect or barrier formation at the grain joints. At the same time, M2O brings the special properties. They can be involved in specific chemical interactions with the particular gas.
Presentation: oral at E-MRS Fall Meeting 2004, Symposium A, by Marina N. Rumyantseva
See On-line Journal of E-MRS Fall Meeting 2004
Submitted: 2004-04-30 11:19 Revised: 2009-06-08 12:55