Zirconia sensors

J. W. Butier and co-workers, FastKesponse Zirconia Sensor-Fased Instrument for Measurement of the Air (Fuel Katio of Combustion Exhaust, SAE 840061, Society of Automotive Engineers, Warrendale, Pa., 1984. 

FIGURE 13.52 (a) Solid electrolyte and (b) arrangement of the zirconia sensor. 

The principle of their operation is the same, but the method of implementation of the sensor is largely dependent on the conditions of the application. Thus, a zirconia sensor for measurement of 02 in molten steel (1,600°C) has to be designed in such a way that the thermal expansion coefficients of the different layers in this device are matched. On the other hand, a room-temperature potentiometric oxygen sensor can be constructed (Yamazoe et al., 1987) by using another set of materials ... 

The zirconia sensor operates primarily on the principle of a concentration cell. It consists of a non-porous solid electrolyte layer fabricated from zirconia stabilized with yttria or calcia and exhibits high oxygen ion mobility. This layer is sandwiched between two porous and electrically conductive electrodes. 

Such stabilized zirconia sensor devices are widely used for combustion control in automobiles. All new cars sold in the US contain one of these devices in the exhaust system to sense the partial pressure of oxygen. This sensor is a key component... 

Zirconia sensors have been used primarily in the exhaust system of automobiles to control the air-to-fuel ratio for meeting the federal requirements on such noxious gases as carbon monoxide, methane and nitrogen oxides. The applicability of zirconia sensors for this particular application is based on the assumption that, under thermodynamic equilibrium, the partial pressure of oxygen in the exhaust gas depends primarily on the air-to-fuel ratio. To compensate for the fact that in reality equilibrium is not reached, catalytic platinum electrics are incorporated in the zirconia sensor design [Stevens, 1986]. In the zirconia sensor, the outside of the zirconia tube is exposed to the exhaust gas while the inside is exposed to the ambient air as a reference atmosphere. 

Vogel, A., Baier. G. and Schiile, V. (1993) Non-Nernstian potentiometric zirconia sensors Screening of potential working electrode materials. Sens. Actuators B, 15-16. 147-50. 

Miura, N., Warrg, J, Nakatou, M., Elumalai, P. and Hasei, M. (2005) NO sensirrg characteristics of mixed-potential-type zirconia sensor using NiO sensirrg electrode at high temperatures. Electrochem. Solid-State Lett., 8 (2), H9-11. 

Martin, L.P., Pham, A.Q. and Glass, R.S. (2003) Effect of Cr2O3 electrode morphology on the nitric oxide response of a stabilized zirconia sensor. Sens. Actuators B, 96, 53-60. 

Hibino, T, Kuwahara, Y, Wang, S., Kakimoto, S. and Sano, M. (1998) Nonideal electromotive force of zirconia sensors for unsaturated hydrocarbon gases. Electrochem. Solid-State Lett., 1 (4). 197-9. 

G. and Salatino, P. (2006) Assessment of gas-fiuidized beds mixing and hydrodynamics by zirconia sensors. AIChEJ., 52 (1), 185-98. 

MODELING INTERACTIONS OF OXYGEN WITH THE ZIRCONIA SENSOR... 

MODELING INTERACTIONS OF VARIOUS GASES WITH NON-NERNSTIAN ZIRCONIA SENSORS... 

It is noteworthy that the surface chemistry of zirconia sensors under practical operating conditions is much more complicated than expected from the oxygen partial pressures in a simple Equation (3.3). This equation imphes that only oxygen is involved in the potential forming electrode reaction, whereas in reality, a series of electrode reactions occurs together with Equation (3.1) on the SE [8] ... 

When the zirconia sensor with dissimilar electrodes is exposed to the combustion exhaust, the presence of at least two independent nonequilibrium gases of different... 

It was hrst reported in 2001 [32] that the evaluation by impedance spectroscopy of a biased zirconia sensor with an attached LaFeOa-SE has shown that only the electrode resistance is a function of NO2 content. Consequently, impedance spectroscopy offers a method for directly probing the electrode reactions that are the basis for mixed-potential-type gas sensors [67]. As a result of further development by using impedance spectroscopy in zirconia-based gas sensors with oxide-SEs, a new type of YSZ-based sensor for detecting total NO and HCs at high temperatures has been proposed recently [2, 14, 21, 62, 74, 96-100]. In this case, the change in the complex impedance of the device attached with a specific oxide-SE was measured as a sensing signal. 

Zirconia Sensors for Measurement of Gas Concentration in Molten Metals... 

ZIRCONIA SENSORS FOR THE MEASUREMENT OF OXYGEN ACTIVITY IN MELTS... 

Zirconia Sensors Based on Shaped Eutectic Composites... 

---