High-temperature oxygen sensors based

High-Temperature Oxygen Sensors Based on Electrochemical Oxygen Pumping... 

Menesklou W., Schreiner H.-J., Hardtl K. H., and Ivers-Tiffee E., High temperature oxygen sensors based on doped SrTiOj, Sens. Actuators B, 59,184—189,1999. 

Gerblinger, J., Lohwasser, W, Lampe, U. and Meixner, H. (1995) High-temperature oxygen sensor-based on sputtered cerium oxide . Sensors and Actuators... 

None of the well-known oxygen sensors based on polycrystalline zirconia can survive when the measuring temperature is high and changes so frequently. 

Four solid oxide electrolyte systems have been studied in detail and used as oxygen sensors. These are based on the oxides zirconia, thoria, ceria and bismuth oxide. In all of these oxides a high oxide ion conductivity could be obtained by the dissolution of aliovalent cations, accompanied by the introduction of oxide ion vacancies. The addition of CaO or Y2O3 to zirconia not only increases the electrical conductivity, but also stabilizes the fluorite structure, which is unstable with respect to the tetragonal structure at temperatures below 1660 K. The tetragonal structure transforms to the low temperature monoclinic structure below about 1400 K and it is because of this transformation that the pure oxide is mechanically unstable, and usually shatters on cooling. The addition of CaO stabilizes the fluorite structure at all temperatures, and because this removes the mechanical instability the material is described as stabilized zirconia (Figure 7.2). 

Another type of high temperature solid state O2 sensor that has been developed is based on the principle of electrochemical pumping of oxygen with Zr02 electrolytes. These sensors have higher sensitivity (generally, a first power dependence on Pq) than the Nernst cell and the resistive device and possess a number of other characteristics that make them very promising for many new applications. 

Another type of sensor is a high-temperature solid-state potentiometric sensor for oxygen (>400°C) in industrial processes. These are based on the measurement of the potential of a concentration cell of the type... 

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