Development of a solid electrolyte sensor for oxygen in hot gases

High-temperature oxygen detection is used in the emission control and optimization of combustion and metallurgic processes. To overcome the disadvantages of potentiometric sensors, we have investigated an actively operated three-electrode system on yttria-stabilized zirconia solid electrolyte. At various selected potentials, there is a strong and stable relationship between the current and the concentration of gaseous oxygen. The current is not limited by the gas diffusion and is, therefore, unaffected by the gas flow. It is demonstrated that the electrode and electrolyte degradation can be considerably retarded by the proper selection of the electrode voltage profile. A metal-film resistance thermometer deposited directly on the sensor is found to be suitable for the on-site temperature monitoring. This sensor also responds to combustion products present in a hot gas. A possible development of a multicomponent sensor is discussed.