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

A porous composite electrode of La_0.8Sr_0.2Cr_0.97V_0.03O_{3 -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 600º C and 900º 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 700º 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 800º C, gas phase mass transport processes dominate the impedance spectra. The relatively low response time at 700º 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.