SURFACE MODIFICATION OF SOLID ELECTROLYTES FOR GAS SENSORS

Surface modifications allow to use fast solid ionic conductors for gas sensors without requiring the transfer of the gaseous species (or their presence as an immobile component). A mixed ionically and electronically conducting layer directs the cell reaction in such a way that both the gaseous species and the electroactive component become involved. Examples are given for Cl2, O2 and NO2 partial-pressure measurements. The reaction may be controlled by kinetic parameters which leads to deviations from thermodynamically expected values. Kinetic phenomena may be employed advantageously to discriminate between several gases. Selectivity, stability ranges and response times of surface modified gas sensors are discussed. © 1990.