OXYGEN GAS SENSORS BASED ON CEO2 THICK AND THIN-FILMS

Ceria is a promising material for resistive-type oxygen exhaust gas sensors. This paper describes the preparation of ceria thick and thin films and the development of prototype sensors with an additionally integrated platinum temperature sensor and a sensor heater. The CeO2 films exhibit very good adhesion, high thermal shock resistance and no apparent aging under changing gas compositions and at temperatures up to 1000-degrees-C. The electrical conductivity of CeO2 films as a function of the oxygen partial pressure and the temperature behaves analogously to that of bulk material. In a comparison of model calculations with measured data, it is shown that, depending on the material composition, CeO2 sensors are suitable for closed-loop combustion control of stoichiometric or lean air/fuel mixtures. Response times from 5 to 10 ms can be realized with thin- or thick-film CeO2 sensors.