“NO-selective” NOx sensing elements for combustion exhausts

Fabrication and characterization of NOx sensing elements using co-planar oxide and Pt electrodes is described. The sensing elements, based on yttria-stabilized zirconia substrates, could be current-biased to a “NO-selective” sensing condition (for NOx in the concentration range 50-1500 ppmV) if the oxide was an alkaline earth-modified lanthanum chromite. Simple variations in electrode geometry (interdigitation of the electrodes or increase of the oxide electrode surface area relative to the Pt electrode) did not affect the magnitude of the NO response or the recovery from exposure to NO. The main effects of temperature appeared to be a decrease in the response magnitude with increasing T and an increase of the recovery time (from NO exposure) with decreasing T.