Gas sensor applications of oxygen-ionic electrolytes: Development of their electron model

The objective of the present paper is to provide an electron model of the solid electrolytes with oxygen-ionic conductivity for gas sensors to simulate contact phenomena on the boundary of stabilized zirconia/metal electrode interface within the solid state zone theory. The primary focus of this article is modelling and assessment of the ability of yttria-stabilized zirconia (YSZ)-based solid electrolyte to control oxygen potentials at low temperatures in different environments. The proposed model allows the necessary information with regard to the electrolyte/metal electrode interface and about the character of the electronic conductivity to be obtained. The model also describes that the character of the electronic conductivity in solid electrolytes usually depends on two mechanisms of charge transfer: electrons transfer in the conductivity zone, separated from the valent zone in the solid electrolyte by the wide enough forbidden zone and the spasmodic transitions of electrons from one local level to another within the forbidden zone. Based on the proposed model, it was found that even the small traces of metallic admixtures in the solid oxygen-ionic electrolytes can substantially reduce the limits of the electrolytes applicability both by temperature and the level of measuring partial pressure.