NOx response properties in DC current of Nd2CuO4/4YSZ/Pt element

The NOx response properties in dc current of an Nd2CuO4/Y2O3 (4 mol%)-stabilized ZrO2 (4YSZ)/Pt element were investigated in both air and 5 %O-2-N-2 mixed gas at 400 degrees C. The current increased in proportion to the logarithm of NOx concentration, even when two electrodes were exposed to the same atmosphere. When Nd2CuO4 was used as the cathode, the ratio of current in NOx to that in carrier gas at 1 V was larger for NO2 than that for NO and not affected by the variation of oxygen concentration within 5 to 20% in carrier gas. In contrast, when Pt was used as the cathode, the current ratio was dependent on the oxygen concentration. Impedance analysis showed decreases in resistance and capacitance at the electrolyte/electrode interfaces with the introduction of NOx gas. The possibility of a NOx gas sensor unaffected by ambient oxygen concentration was suggested.