Metal oxide solid electrolytes yttria-stabilized zirconia

The net result is the formation of a dense and uniform metal oxide layer in which the deposition rate is controlled by the diffusion rate of ionic species and the concentration of electronic charge carriers. This procedure is used to fabricate the solid electrolyte yttria stabilized zirconia (YSZ). 

Another application is in the oxidation of vapour mixtures in a chemical vapour transport reaction, the attempt being to coat materials with a thin layer of solid electrolyte. For example, a gas phase mixture consisting of the iodides of zirconium and yttrium is oxidized to form a thin layer of yttria-stabilized zirconia on the surface of an electrode such as one of the lanthanum-strontium doped transition metal perovskites Lai Sr MO --, which can transmit oxygen as ions and electrons from an isolated volume of oxygen gas. 

It has been observed that solid oxide fuel cell voltage losses are dominated by ohmic polarization and that the most significant contribution to the ohmic polarization is the interfacial resistance between the anode and the electrolyte (23). This interfacial resistance is dependent on nickel distribution in the anode. A process has been developed, PMSS (pyrolysis of metallic soap slurry), where NiO particles are surrounded by thin films or fine precipitates of yttria stabilized zirconia (YSZ) to improve nickel dispersion to strengthen adhesion of the anode to the YSZ electrolyte. This may help relieve the mismatch in thermal expansion between the anode and the electrolyte. 

In order to address both fundamental and application aspects of electrochemical promotion in this Chapter, the combustion of ethylene over Ir02 or RUO2 catalysts and the reduction of NO with propylene over Rh catalysts —all deposited on yttria-stabilized zirconia (YSZ) solid electrolyte— have been chosen as model catalytic systems. While the literature of electrochemical promotion deals mainly with metal catalysts, our laboratory has a long experience with promotion of metal oxide catalysts, such as Ir02 and RUO2. In fact, ethylene combustion with Ir02/YSZ film catalyst was the first catalytic system found to exhibit the phenomenon of permanent electrochemical promotion, which manifests itself as a shift in the steady-state open-circuit activity due to polarization, and is attributed to a change in... 

At even higher temperatures in the range of 800-900 °C, ionic conduction can also be observed in solid oxides. Certain doped metal oxides become conductors hence, they can be utilized as electrolytes in the solid oxide fuel cell (SOFC). The most common oxide used is yttria-stabilized cubic zirconia (Zr02), called YSZ, with a doping level of 8% Y2O3. This material is a ceramic the thermal expansion coefficient of its thin layers has to be matched with the other fuel cell components. 

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