Composite Sr- and V-doped LaCrO3/YSZ sensor electrode operating at low oxygen levels

A porous composite electrode of La0.8Sr0.2Cr0.97V0.03O3 -delta (LSCV) and yttria-stabilised zirconia (YSZ) was evaluated as a possible candidate for high-temperature potentiometric oxygen sensor measuring electrodes. The oxygen processes at the electrode were characterised by performing electrochemical impedance spectroscopy (EIS) measurements between 600 A degrees C and 900 A degrees C at oxygen partial pressures between 4.2x10 (-6) and 0.2 bar. The microstructure of the electrode was characterised by electron microscopy. The LSCV/YSZ electrode was porous and coherent with LSCV and YSZ grain sizes between 200 and 400 nm. At oxygen partial pressures around 0.2 bar at 700 A degrees C, the oxygen reaction is dominated by solid-state diffusion of oxide ions and surface reaction kinetics. At oxygen partial pressures around 10 (-5) bar above 800 A degrees C, gas phase mass transport processes dominate the impedance spectra. The relatively low response time at 700 A degrees C at an oxygen partial pressure of around 5x10 (-6) bar and an inlet gas flow rate of 8 L h(-1) makes the LSCV/YSZ electrode suitable for use as an potentiometric oxygen sensor electrodes.