Some attempts at developments and analyses of oxygen sensors are presented with a review in this field. For oxygen concentration cell type zircornia sensors for stoichiometric A/F control, its mechanism is discussed and a unified explanation is proposed.
For oxide semiconductor type oxygen sensors, TiO2, Nb2O5 and CeO2 sensors are described with an emphasis on a recently developed Nb2O5 thin film oxygen sensor. Several types of lean A/F sensors are also discussed. Of these sensors, oxygen sensors which utilize the electrochemical pumping action of a solid electrolyte are preferable.