Equivalent circuit analysis on NOx impedance-metric gas sensors

This study deals with the impedance analysis of NOx sensors. The evaluation of the results is carried out by employing equivalent circuits (ECs). The factors affecting the sensing behavior of the impedance-metric sensors towards NO and NO2 are not fully understood. In order to provide comparable results the analysis were focused on determination of the characteristics with different combination of sensor elements. The obtained impedance spectra were correlated to sensor electrode layers, electrode/electrolyte interfaces and the mechanisms and electrochemical reactions taking place at those by changing the atmospheres and sensor setups. An EC has been designed with the help of which the measured spectra were fitted. The CNLS (complex non-linear least square) analysis of the proposed EC delivers good results. It was shown that, the equivalent circuit analyses combined with present sensing theories enlighten with some possible explanations the sensing behavior of impedance-metric gas sensors.