Yttria-stabilized Zirconia Solid Electrolyte Research Articles

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

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.

ChemInform Abstract: OXYGEN DIFFUSION IN VAPOR‐DEPOSITED INDIUM OXIDE FILMS

AbstractAuf ZrO,: Y2O3‐ Substraten aufgedampfte lngOg‐Filme transportieren Sauerstoff zwischen 1000 und 1300 K und 1 at O2 ‐Druck über einen Zwischengittermechanismus, während bei sehr geringen PO2 ( S 1 Pa) ein Leerstellenmechanismus zu wirken beginnt.

Oxygen Diffusion in Vapor‐Deposited Indium Oxide Films

Diffusion measurements were made between 1000 and 1300 K on films of In2O3 by electrochemical techniques using an yttria‐stabilized zirconia solid electrolyte. At atmospheric oxygen pressures, diffusion invariably occurred via an oxygen interstitial mechanism. The diffusion coefficient decreased with decreasing oxygen pressure with a PO21/2 dependence. Near 1.0 Pa PO2the mechanism began to change to a vacancy mechanism which dominated at PO2 <10−3 Pa, where diffusivity increased with further decrease in oxygen pressure according to a PO2−1/2 dependence. Activation energies for interstitial and vacancy diffusion were 166 and 190 kJ/mol, respectively.

Electrochemical Transient Investigations of the Diffusion and Concentration of Electrons in Yttria Stabilized Zirconia-Solid Electrolytes

Abstract The voltage relaxation of galvanic cells with zirconia electrolytes polarized between an inert silver electrode and an Fe + FeO electrode has been analyzed to obtain the diffusion coefficient of the electronic minority charge carriers in the temperature range between 700 and 900 °C. The method has been examined by using different thicknesses of the sample. At 800 °C the diffusion coefficient of the electrons is 1.4 × 10-3 cm2 /sec, i.e., about two orders of magnitude higher than that for the holes, 4.5 × 10-6 cm2/sec. The activation energy 0.55 eV is obtained for the electrons, compared to 1.4 eV for the holes. From conductivity data, the concentrations of electrons and holes at 800 °C and 1 atm oxygen partial pressure are calculated to be 1 × 109 and 4 × 1017 cm-3, respectively. The electronic band gap is evaluated to be 4.1 eV.