A FIRST PRINCIPLES MODEL OF METAL-OXIDE GAS SENSORS FOR MEASURING COMBUSTIBLES

A first principles model is described for the operation of electrochem ical type sensors designed to measure combustibles in air. It is based on the general principles presented in previous publications (A.D. Br ailsford, E.M. Logothetis, Sens. Actuators, 7 (1985) 39-67; A.D. Brail sford, M. Yussouff, E.M. Logothetis, Sens. Actuators, B 13 (1993) 135- 138; A.D. Brailsford, RI. Yussouff, E.M. Logothetis, M. Shane, Sens. A ctuators, B 24-25 (1995) 362-365; A.D. Brailsford, M. Yussouff, E.M. L ogothetis, Sens. Actuators B 34 (1996) 407-411; and A.D. Brailsford, M . Yussouff, E.M. Logothetis, Sens. Actuators, B 35-36 (1996) 392-397) for an ab initio model developed to describe the operation of metal ox ide oxygen sensors. The authors show that the e.m.f. of the combustibl es sensor may be written as the difference between the e.m.f.s of two non-identical air-referenced oxygen sensors. This helps in the qualita tive understanding of the observed and predicted responses of the comb ustibles sensors. The present model is used to analyze experimental da ta reported in the literature (H. Okamoto, H. Obayashi, T. Kudo, Solid State Ion. I (1980) 319-326; and A. Vogel, G. Baler, V. Schuele, Sens . Actuators B 15 (1993) 147-150) and to indicate the variety of behavi or expected from these sensors depending on the properties of the elec trode materials. This analysis is expected to aid the design and optim ization of these sensors. (C) 1998 Published by Elsevier Science S.A. All rights reserved.