Doping and defect association in oxides for use in oxygen sensors

Oxygen sensors provide valuable information for improving the efficiency of, and thus reducing harmful emissions from, combustion processes, such as in internal combustion engines. Oxide materials can be used in different ways to generate an oxygen partial pressure dependent output. The type of sensor in which a particular oxide is used depends on the ionic and electronic defects in the oxide, which can be, to some extent, controlled by doping. In this paper, the issues in selection of an oxide for use in resistive-type, potentiometric-type and amperometric-type oxygen sensors are reviewed. Prototypical examples of materials, specifically titania and zirconia, commonly used in these sensors are discussed to illustrate the effects of doping and defect interaction on the electrolytic and transport properties of oxide materials for use in oxygen sensors. (C) 2003 Kluwer Academic Publishers.