Solid Electrolyte-Based Electrochemical Sensors

Korotcenkov, Handbook of Gas Sensor Materials, Integrated Analytical Systems, 

Gas Sensor structure Air, RE 1 electrolyte SE, target gas Sensitivity, mV/decade Gas cone, (ppm) T (°C) 

Source data from Liang et al. (2012), etc. RE reference electrode, SE sensing electrode 

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Park CO, Akbar SA, Weppner W (2003) Ceramic electrolytes and electrochemical sensors. J Mater Sd 38 4639- 660 Park CO, Fergus JW, Miura N, Park J, Choi A (2009) Solid-state electrochemical gas sensors. Ionics 15 261—284 Patil LA (2009) FCjOj - ZnO based gas sensors. Sens Transducers J 104(5) 68-75... 

Nikolova V, Nikolov I, Andreev P, Najdenov V, Vitanov T (2000) Tungsten carbide-based electrochemical sensors for hydrogen determination in gas mixtures. J Appl Electrochem 30 705-710 Ogura K, Saino T, Nakayama M, Shiigi H (1997) The humidity dependence of the electrical conductivity of a soluble polyaniline-poly(vinyl alcohol) composite film. J Mater Chem 7 2363-2366 Opekar F (1992) An amperometric solid-state sensor for nitrogen dioxide based on a solid polymer electrolyte. Electroanalysis 4 133-138... 

Electrochemical cells where ions dissipate through a solid electrolyte are mainly used for measuring oxygen concentrations. The most common sensors based on this principle are the A-probe for monitoring combustion engines in motor vehi-... 

On the other hand, the theoretical performance of concentration electrochemical cells, based on perovskite materials with protonic and oxygen ion conduction properties, has been described as well [191]. Besides, a sensor for the detection of oxidizable gases that employs the production of a non-Nemstian electrode potential, using zirconia as the solid electrolyte, has been developed [192],... 

This anodic reaction provides sodium ions and electrons to the solid electrolyte and the inert Pt counter electrode, respectively, at the source side. Both the sodium ions and electrons will then travel through the solid electrochemical cell along previously-mentioned ionic and electronic paths to sustain the PEVD cathodic reaction for Na COj product formation at the sink side. Eurthermore, based on anodic reaction 60, the chemical potential of sodium is fixed by the vapor phase at the source side. Under open circuit conditions, this type of source can also serve as the reference electrode for a CO potentiometric sensor. 

The nonequilibrium potentials measured in solid-electrolyte cells are established by electrochemical reactions, just as for equilibrium-based sensors. For example, in an environment containing CO and O2, the CO could be oxidized chemically according to the following reaction ... 

Imanaka, N., Oda, A., Tamura, S. and Adachi, G.-Y. (2004) Total nitrogen oxides gas sensor based on solid electrolytes with refractory oxide-based auxiliary electrode. J. Electrochem. Soc., 151 (5), H113-16. 

Yao, S. and Stetter, J.R. (2005) Solid-state NOx sensor based on surface modifications of the solid electrolyte. Proceedings of the Electrochemical Society, 2000-52 Solid-State Ionic Devices II Ceramic Sensors, The Electrochemical Society, Pennington. New Jersey, pp. 252-60. 

Wang, L. and Kumar. R.V. (2006) Potentiometric SO2 gas sensor based on a thick film of Ca ion conducting solid electrolyte. J. Appl. Electrochem., 36, 173-8. 

Imanaka, N., Kamikawa. M.. Tamura. S. and Adachi, G. (1999) CO2 sensor based on the combination of trivalent Sc ion-conducting Sc2(WO4) and O ion-conducting stabilized zirconia solid electrolytes. Electrochem. Solid-State Lett., 2 (11), 602-4. 

Mukundan, R.. Brosha, E.L., Brown, D.R. and Garzon, F.H. (1999) Ceria-electrolyte-based mixed potential sensors for the detection of hydrocarbons and carbon monoxide. Electrochem. Solid-State Lett.. 2 (12), 412-14. 

Miura, N. and Yamazoe, N. (2001) Approach to high-performance electrochemical NOx sensors based on solid electrolytes. Sensors Update, 6, 191-210. 

FIGURE 2.3 Schematic presentation of the interaction of the solid electrolyte oxygen sensor with gas environment 1-6 stages of interaction. (From Zhniykov, S., Mathematical model of electrochemical gas sensors with distributed temporal and spatial parameters and its transformation to models of the real YSZ-based sensors. Ionics 12 (2006) 135-148. With kind permission of Springer Science and Business Media.)... 

When zirconia-based electrolytes are exposed to the high temperatures (T > 1100°C) and low oxygen partial pressures P02 < 10 ° Pa), usually encountered in metal melts, they exhibit mixed ionic and n-type electronic conductivities. Under these conditions, the solid electrolyte sensor generates cm/that is influenced by the electrical properties of the solid electrolyte. Schmalzried [25] has analyzed the contribution of electronic conductivity in the zirconia electrolytes to the measured emf of an electrochemical cell in the P02 region less than 10 Pa and has shown that, in the presence of n-type electronic conductivity, the emf of the sensor can be expressed as... 

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. 

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