Investigation of an Impedimetric LaSrMnO(3)-Au/Y(2)O(3)-ZrO(2)-Al(2)O(3) Composite NO(x) Sensor

Composite NO(x) sensors were fabricated by combining partially and fully stabilized yttria-doped zirconia with alumina forming a composite electrolyte, Y(2)O(3)-ZrO(2)-Al(2)O(3), and strontium-doped lanthanum manganese oxide mixed with gold to form the composite sensing electrode, La(0.8) Sr(0.2)MnO(3)-Au. A surface chemistry analysis of the composite sensor was conducted to interpret defects and the structural phases present at the Y(2)O(3)-ZrO(2)-Al(2)O(3) electrolyte, as well as the charge conduction mechanism at the LaSrMnO(3)-Au electrode surface. Based on the surface chemistry analysis, ionic and electronic transport properties, and microstructural features of sensor components, the working principle was described for NO(x) sensing at the composite sensor. The role of the composite materials on the NO(x) sensing response, cross-sensitivity to O(2), H(2)O, CO, CO(2), and CH(4), and the response/recovery rates relative to sensor accuracy were characterized by operating the composite [Formula: see text] sensors via the impedimetric method. The composite sensors were operated at temperatures ranging from 575 to 675 °C in dry and humidified gas environments with NO and NO(2) concentrations varying from 0 to 100 ppm, where the balance gas was N(2). It was found that the microstructure of the composite NO(x) sensor electrolyte and sensing electrode had a significant effect on interfacial reactions at the triple phase boundary, as well as the density of active sites for oxygen reactions. Overall, the composite NO(x) sensor microstructure enabled a high NO(x) sensing response, along with low cross-sensitivity to O(2), CO, CO(2), and CH(4), and promoted NO detection down to 2 ppm.