Electrode material for high-temperature oxygen partial pressure electrochemical sensors: Strontium-doped lanthanum chromite

Abstract

The electrochemical behavior of 20% strontium-doped lanthanum chromite (SDLC), deposited onto a 8% yttria-stabilized zirconia (YSZ) solid electrolyte, has been investigated. The electromotive force developed across the interface SDLC/YSZ and a Pt/YSZ reference at 0.21 atm (air) corresponds to the Nernst theoretical relationship. This behavior has been tested between 700° and 1000 °C in the ranges 100–10−5 and 10−13–10−20 atm of oxygen, the lower pressures by the equilibrium of carefully calibrated steam and hydrogen mixtures. Although not demonstrated, it is probable that the oxygen pressure range of applicability of this mixed oxide electrode covers the entire field of pure ionic conductivity of any zirconia-base electrolyte. The fair agreement between the measured values and the theoretical emf values, the resistance of the electrode layer to scaling, as well as its good thermodynamic stability, suggests SDLC as a possible alternative to platinum in high-temperature oxygen pressure sensors.