INVESTIGATIONS ON THE DETERMINATION OF NO WITH GALVANIC ZRO2 SOLID-ELECTROLYTE CELLS

In order to demonstrate the usefulness of gas-symmetrical galvanic ZrO 2 solid electrolyte cells for the determination of NO, cell tensions c aused by catalytically different active electrodes and thereby differe nt oxygen partial pressures in N2/NO mixtures with a low oxygen concen tration (< 50 vol.-ppm) were measured in the temperature range of 500 to 800-degrees-C. Separate investigations demonstrated that the cataly tic activity of Pt decreases with increasing sinter temperature (1000 to 1300-degrees-C), but is higher than the activity of perovskite type oxides La1-xSrxMeO3 (x = 0.1....0.5; Me = Co, Mn, Fe, Cr). The activi ty of the perovskites decreases in the order Co>Mn almost-equal-to Fe> Cr. Between different Pt electrodes changes of cell tension were measu red when alternating between pure and NO containing nitrogen (e.g. 19. 7 mV with 0.4 vol.-% NO). Cells with a Pt electrode and a perovskite e lectrode produce higher changes of the cell tension, but without going to zero in pure nitrogen due to own oxygen potentials of the mixed ox ides.