Impedance As a Diagnostic Tool to Characterize Mixed-Potential Sensor Response

Commercial tape casting and screen-printing methods have been used to fabricate a planar, self-heated, mixed-potential NOx sensor for application in vehicle on-board emission control systems. The device consists of dense La0.8Sr0.2CrO3 (LSCrO) and Pt electrodes and a porous YSZ electrolyte on one side of a dense ceramic substrate and a Pt-heater with independent leads on the backside of the substrate. While these sensors have demonstrated high sensitivity and selectivity to NOx when operated at a positive bias, optimization of the sensor device geometry remains an open question. In this work, we used circular cells of dense YSZ with LSCrO working and Pt counter electrodes in order to identify the impedance response of each individual sensor component. The impedance response measured on the cell was then used to identify the rate-limiting processes underlying the response of the planar sensor device.