Investigations of conduction mechanism in Cr2O3 gas sensing thick films by ac impedance spectroscopy and work function changes measurements

This paper investigates the conduction mechanism in Cr2O3 gas sensing thick films. A citrate combustion method was used for the preparation of the metal oxide and ethanol vapour as a test gas. The manner in which surface reactions induced electrical changes are affecting the sensor signals inputs was explored by simultaneous dc and work function changes (Kelvin probe method). The identification of the contributions to conduction of the different sensing layer elements was made possible by ac impedance spectroscopy measurements. A conduction model, which qualitatively explains the experimental findings, was elaborated on the basis of the acquired experimental data and the information provided in literature. The model validity should apply, besides Cr2O3, to all p-type metal oxides used as gas sensitive materials.

[1]  A. Holt,et al.  Electrical conductivity and defect structure of Mg-doped Cr2O3 , 1997 .

[2]  David E. Williams,et al.  Description and characterization of a hydrogen sulfide gas sensor based on Cr2-yTiyO3+x , 1995 .

[3]  S. Morrison.  Surface states on a chromia catalyst , 1977 .

[4]  L. Cojocaru.  Electrical Properties of Non-Stoichiometric Cr2O3 , 1969 .

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

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

[7]  Richard M. Lambert,et al.  Interaction of oxygen with chromium(III) oxide: chemisorption studies and the effects of surface additives , 1986 .

[8]  S. R. Morrison,et al.  The Chemical Physics of Surfaces , 1977 .

[9]  P. T. Moseley,et al.  A selective ammonia sensor , 1990 .

[10]  Udo Weimar,et al.  A.c. measurements on tin oxide sensors to improve selectivities and sensitivities , 1995 .

[11]  G. Spoto,et al.  Revisiting the α-Cr2O3/CO interaction: an FTIR and HRTEM study , 1993 .

[12]  J. T. Ranney,et al.  The Surface Science of Metal Oxides , 1995 .

[13]  U. Weimar,et al.  Understanding the fundamental principles of metal oxide based gas sensors; the example of CO sensing with SnO2 sensors in the presence of humidity , 2003 .

[14]  D. Cox,et al.  α-Cr2O3 (1012) : surface characterization and oxygen adsorption , 1999 .

[15]  Ivan P. Parkin,et al.  A simple equivalent circuit model to represent microstructure effects on the response of semiconducting oxide-based gas sensors , 2003 .

[16]  B. Weckhuysen,et al.  Alkane dehydrogenation over supported chromium oxide catalysts , 1999 .

[17]  S. Morrison,et al.  Chromium oxide gas sensors for the detection of hydrogen, oxygen and nitrogen oxide , 1994 .

[18]  David E. Williams,et al.  Resolving combustible gas mixtures using gas sensitive resistors with arrays of electrodes , 1996 .

[19]  A. Holt,et al.  Electrical conductivity of Cr2O3 doped with TiO2 , 1999 .

[20]  David E. Williams,et al.  Selectivity and composition dependence of response of gas-sensitive resistors. Part 2.—Hydrogen sulfide response of Cr2 –xTixO3 +y , 1995 .

[21]  L. Manzer,et al.  Catalytic synthesis of chlorofluorocarbon alternatives , 1993 .

[22]  Y. Shimizu,et al.  NOx Sensing Properties of Varistor-Type Gas Sensors Consisting of Micro p-n Junctions , 2001 .

[23]  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 .