The operational characteristics of an oxygen pump using Cu substituted bismuth vanadate, BICUVOX.1, solid electrolyte for an open system was investigated in detail. The major objectives were to show a correlation between oxygen pumping current and cell voltage, Faradic efficiency, oxygen production rate, and to investigate structural stability of the solid electrolyte under current flow. The dc polarization diagram showed four different, well defined regions. They correspond to the electron transfer reaction and Ohm'ic resistance of the electrode and electrolyte respectively. The last two regions at high current densities showed a progressive deviation from the Ohm'ic behavior and finally voltage instability. These were considered to be the result of current induced structural modification, which was detected by X-ray analysis of cathode and anode side separately. The oxygen production rate was examined for different temperatures (450 to 550 degrees C). It increased by increasing the current density up to 800 mA/cm(2), where instability in cell potential was observed, and the Faradic efficiency was declining slightly from100 to 95%. (c) 2006 Springer Science + Business Media, Inc.