Modeling of hydrocarbon sensors based on p-type semiconducting perovskites.

In the scope of the present contribution, perovskite SrTi(1-x)Fe(x)O(3-delta) was investigated as a model material for conductometric hydrocarbon sensing at intermediate temperatures between 350 and 450 degrees C. To explain the observations made during sensor optimization in a quantitative way, a novel sensor model was proposed. At the microscopic scale, the local gas concentration affects local conductivity of the gas sensitive material. In the case of n-type tin oxide sensors, this interaction is commonly attributed to a redox reaction between the reducing analyte gas and adsorbed oxygen. In contrast, a reduction process affecting the entire bulk was assumed to govern gas sensitivity of SrTi(1-x)Fe(x)O(3-delta) films. Although very few variables needed to be assumed or fitted, the present bulk-type model was found to represent well sensor functionality of p-type conducting SrTi(0.8)Fe(0.2)O(3-delta) films. In addition to the temperature dependence of sensor response, the hydrocarbon sensitivity, m, was predicted with good accuracy. The different sensor responses towards hydrocarbons with a different chemical reactivity and other cross-interfering species, such as NO, was explained as well as the dependence on film thickness for screen printed films.

[1]  David E. Williams.  Semiconducting oxides as gas-sensitive resistors , 1999 .

[2]  Ralf Moos,et al.  Hydrocarbon sensing with thick and thin film p-type conducting perovskite materials , 2005 .

[3]  K. Westerterp,et al.  Industrial catalysis : optimizing catalysts and processes , 1998 .

[4]  N. Yamazoe,et al.  Study of metal oxide catalysts in the olefin oxidation from their reduction behavior: I. Reduction of various metal oxides with propylene , 1979 .

[5]  I. Metcalfe,et al.  Solid Electrolyte Potentiometric Study of La(Sr)Mno3 Catalyst During Carbon-Monoxide Oxidation , 1995 .

[6]  J. Maier,et al.  Defect association in acceptor-doped SrTiO3: case study for Fe′TiV˙˙O and Mn″TiV˙˙O , 2003 .

[7]  S. Morrison.  Selectivity in semiconductor gas sensors , 1987 .

[8]  Ralf Moos,et al.  Selectivity enhancement of p-type semiconducting hydrocarbon sensors—The use of sol-precipitated nano-powders , 2008 .

[9]  J. Maier,et al.  Oxygen incorporation into Fe-doped SrTiO3: Mechanistic interpretation of the surface reaction , 2002 .

[10]  T. Wolkenstein,et al.  Electronic Processes on Semiconductor Surfaces during Chemisorption , 1991 .

[11]  A. Atkinson,et al.  Defect properties of Ti-doped Cr2O3 , 2006 .

[12]  Solid Electrolyte Potentiometry Aided Studies of Oxidic Catalysts , 2004 .

[13]  S. Morrison,et al.  Semiconductor gas sensors , 1985 .

[14]  Kengo Shimanoe,et al.  Theory of gas-diffusion controlled sensitivity for thin film semiconductor gas sensor , 2001 .

[15]  N. Bârsan,et al.  Conduction Model of Metal Oxide Gas Sensors , 2001 .

[16]  C. Varenne,et al.  Gas sensing properties of pseudo-Schottky diodes on p-type indium phosphide substrates: Application to O3 and NO2 monitoring in urban ambient air , 2002 .

[17]  Ralf Moos,et al.  Materials for temperature independent resistive oxygen sensors for combustion exhaust gas control , 2000 .

[18]  C. Richard A. Catlow,et al.  Experimental and computational study of the gas-sensor behaviour and surface chemistry of the solid-solution Cr2−xTixO3(x≤ 0.5) , 2002 .

[19]  Ralf Moos,et al.  Effect of electrodes and zeolite cover layer on hydrocarbon sensing with p-type perovskite SrTi0.8Fe0.2O3-δ thick and thin films , 2006 .

[20]  L. N. Yannopoulos.  A p-type semiconductor thick film gas sensor , 1987 .

[21]  Ralf Moos,et al.  Temperature-independent resistive oxygen exhaust gas sensor for lean-burn engines in thick-film technology , 2003 .

[22]  Giuliano Martinelli,et al.  Gas-sensitive electrical properties of perovskite-type SmFeO3 thick films , 1998 .

[23]  P. Meuffels.  Propane gas sensing with high-density SrTi0.6Fe0.4O(3−δ) ceramics evaluated by thermogravimetric analysis , 2007 .