Electrochemical device for the precise adjustment of oxygen partial pressures in a gas stream

For investigations of the defect chemistry and the transport properties of oxides conductivity measurements as a function of oxygen partial pressure and temperature are commonly applied. While precise temperature control with an accuracy better than ±0.1 °C can easily be realised, stable oxygen partial pressures, e.g. between about 10−5 and 10−16 bar at T=700 °C, cannot be achieved in a gas stream by simple gas mixing methods. We constructed an electrochemical cell consisting of a tube of platinum-coated yttria-stabilised zirconia (YSZ), a miniaturised oxygen sensor positioned close to the sample within the YSZ-tube and an electronic process controller enabling the precise adjustment of oxygen partial pressures stable for more than 24 h between log(pO2/bar)=0 and log(pO2/bar)=−20. The device was tested by conductivity measurements on Fe-doped SrTiO3 (0.1 mol% Fe).