Sensor based on oxygen pumping

Several oxygen sensors based on oxygen pumping with stabilised zirconia have been reported (Hetrick, Fate and Vassell, 1981). This type of oxygen sensor is able to measure the oxygen partial pressure in the exhaust gas from the engine in lean burn. The operating principle of the... 

Logothetis, E.M., Visser, J.H., Soltis, R.E. and Rimai, L. (1992) Chemical and physical sensors based on oxygen pumping with solid-state electrochemical cells. Sens. Actuators B, 9, 183—9. 

Dutta, A. and Ishihara, T. (2005) Amperometric NOx sensor based on oxygen pumping current by using LaCaOj-based solid electrolyte for monitoring exhaust gas. Sens. Actuators B, 108 (1-2), 309-13. 

In the last 20 years, several different types of oxygen sensors based on 02 pumping have been developed(lO). All these sensors have the common characteristic that their signal output is linearly proportional to the ambient oxygen partial pressure. Their other characteristics, however, such as response time, temperature and absolute pressure dependence, and effect of gas flow depend on the specific design and mode of operation of the sensor. 

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

Oxide ion conductors have found widespread apphcations in our modem society. The devices based on oxide ion conductors include oxygen sensors, solid oxide fuel cells (SOFCs), and oxygen pump. 

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. 

These devices are widely used for the control and monitoring of oxygen content in gas mixtures or liquid metals. Usually, the electrochemical pump and oxygen sensor are based on YSZ tubes with platinum electrodes. 

Development of ionic conductors based on stabilized zirconia has reached a level of maturity, where most of the research on such materials concentrates mainly on obtaining incremental empirical improvements in conductivity by better processing control and refinement of the microstructure of the solid electrolyte and SE. Further increases in the conductivity are important in terms of enhancing the efficiency of systems such as O2 sensors, zirconia-based mixed-potential gas sensors, electrochemical oxygen pumps, heating elements, and fuel cells [4-7]. The systematic errors, as have been considered before, are errors with a known determined functional connection with the source of their cause, and the conformity of their appearance can be definitely described. 

Complex FCC oxides of the fluorite type represent oxygen-conduction solid electrolytes (SOE s). They comprise a typical class of materials for the manufacture of sensors of oxygen activity in complex gas mixtures, oxygen pumps, electrolyzers and high-temperature fuel elements. These materials are based on doped oxides of cerium and thorium, zirconium and hafnium, and bismuth oxide. Materials based on zirconium oxide, for example, yttrium stabilized zirconia (YSZ) are the most known and studied among them. This fact is explained both by their processibility and a wide spectrum of practical applications and by the possibility to conduct studies on single crystals, which have the commercial name "fianites" and are used in jewelry. 

Neuymin s research interests were extremely wide. At the early stage he synthesized new solid oxide electrolytes and measured their conductivity and transfer numbers and studied electrode kinetics in the solids. But his main interest was the development of various electrochemical devices based on solid oxide electrolytes, e.g., solid oxide fuel cells (SOFCs), electrolyzers, oxygen pumps, and sensors. From the morning till late in the evening, he was at the institute, and actually he led the laboratory. 

Pump-gauge devices are derived from amperometric and coulometric devices. They consist of a pumping part, to which a variable current can be applied, and a gauge part, which is used for measuring the resulting voltage. Only oxygen sensors are based on this principle. 

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