Sensors impedancemetric

One current-based approach is referred to as impedancemetric sensing [32]. This is based on impedance spectroscopy, in which a cyclic voltage is applied to the electrode and an analysis of the resultant electrical current is used to determine the electrode impedance. As different processes have different characteristic frequencies, impedance spectroscopy can be used to identify and separate contributions from different processes, such as electron transfer at the interface from solid-state electronic conduction. The frequency range ofthe applied voltage in impedancemetric sensors is selected so that the measured impedance is related to the electrode reaction, rather than to transport in the electrode or electrolyte material. Thus, the response is different from that in resistance-based sensors, which are related to changes in the electrical conductivity of a semiconducting material in response to changes in the gas composition. 

The equipment required to analyze the frequency response in impedance spectroscopy is sophisticated, and is thus too expensive to be practical for an operating sensor. In some systems it may be possible to identify a critical frequency (or a limited number of frequencies) that provides the desired response, so that simpler circuitry can be used. However, because of the complicated electronics, impedancemetric sensors are less common than potentiometric sensors. 

Miura, N., Koga, T, Nakatou, M., Elumalai, P. and Hasei, M. (2006) Electrochemical NOx sensors based on stabilized zirconia Comparison of sensing performances of mixed-potential-type and impedancemetric NOx./. Electroceram., 17, 979-86. 

Stranzenbach, M., Gramckow, E. and Saruhan, B. (2007) Planar, impedancemetric NOx-sensor with spinel-type SE for high temperature applications. Sens. Actuators B, 127, 224—30. 

Nakatou, M. and Miura, N. (2005) Detection of combustible hydrogen-containing gases by using impedancemetric zirconia-based water-vapor sensor. Solid State Ionics, 176, 2511-15,... 

Nakatou, M. and Miura, N. (2006) Detection of propene by using new-type impedancemetric zirconia-based sensor attached with oxide sensing-electrode. Sens. Actuators B, 120 (1), 57—62. 

FIGURE 3.1 Catalytic converter system equipped with NO sensors for the exhaust gas emitted from a new-type car engine. (Reprinted from Miura, N., Nakatou M., and Zhuiykov, S., Impedancemetric gas sensor based on zirconia solid electrolyte and oxide sensing electrode for detecting total NO at high temperature. Sens. Actuators B, Chem. 93 (2003) 221-228, with permission from Elsevier Science.)... 

FIGURE 3.23 A SEM (back-scattering) image of a cross-sectional view of a ZnO (+1.5 wt. % Pt)-SE. (Reprinted from Nakatou, M. and Miura, N., Detection of propene by using new-type impedancemetric zirconia-based sensor attached with oxide sensing-electrode. Sens. Actuators B, Chem. 120 (2006) 57-62, with permission from Elsevier Science.)... 

Nakatou, M. and Miura, N., Impedancemetric sensor based on YSZ and InjOj for detection of low concentrations of water vapour at high temperature, Electrochem. Comm. 6 (2004) 995-998. 

Recently, the development of the impedance-based zirconia sensors using the specific spinel-type oxide SE for NO measurement at high temperatures allowed detecting the total NOx concentrations regardless of the NO-NO2 ratio in a gas mixture [55-57]. Development of the impedancemetric NO sensors was described in detail in Chapter... 

Fig. 9.7 Histograms showing (a) typical response of various ordde SEs to 400 ppm NO at 850 °C and (b) relative sensitivity to CjH and CH (400 ppm each) of impedancemetric sensors using each of various single-oxide SEs at 600 °C. Inset shows modeling of complex impedance plots. Points on dashed lines correspond to 1 Hz. (a) Reprinted with permission from Zhuiykov and Miura (2007). Copyright 2007 Elsevier and (b) Reprinted with permission from...

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