Zirconia yttria-stabilized electrolytes

J.K. Hong, I.-H. Oh, S.-A. Hong, and W.Y. Lee, Electrochemical Oxidation of Methanol over a Silver Electrode Deposited on Yttria-Stabilized Zirconia Electrolyte, /. Catal. 163, 95-105 (1996). 

A conductivity cell is set up using an yttria-stabilized zirconia electrolyte. At 900°C the equilibrium pressure in the cell was 1.02 x 10-10 atm, and the reference pressure outside the cell was 7.94 x 10 18 atm. (a) What is the cell voltage The temperature was dropped to 800°C and the reference pressure changed to 1.61 x 10-19 atm. The measured equilibrium voltage was 946 mV. (b) What is the equilibrium oxygen pressure in the cell [Data adapted from D-K. Lee et al., J. Solid State Chem., 178, 185-193 (2005).]... 

Another way to decrease the anodic overpotential is to intercalate a mixed conductor between the yttria stabilized zirconia electrolyte and the metallic anode. Such a combination enlarges the reaction area which theoretically lowers the anodic overpotential. Tedmon et al. [93] pointed out a significant decrease of polarization when ceria-based solid solutions like (Ce02)o.6 (LaO, 5)04 are used as anode materials for SOFCs. This effect is generally attributed to the mixed conductivity resulting from the partial reduction of Ce4+ to Ce3+ in the reducing fuel atmosphere. A similar behaviour was observed in water vapor electrolysis at high temperature when the surface zirconia electrolyte is doped with ceria [94, 95]. 

Hibino, T., Wang, S., Kakimoto, S., and Sano, M. Single Chamber Solid Oxide Fuel Cell Constructed from an Yttria-Stabilized Zirconia Electrolyte, Electrochem. Solid-State Letters, 2, 317 (1999). 

High-temperature stabilized NO-, zirconia potentiometric sensors are also being utilized [187], The electrochemical reactions on zirconia devices take place at the triple-phase boundary, that is, the junction between the electrode, electrolyte, and gas [186], It has been reported that sensors composed of a W03 electrode, yttria-stabilized zirconia electrolyte, and Pt-loaded zeolite filters demonstrate high sensitivity toward NO,, and are free from interferences from CO, propane, and ammonia, and are subject to minimal interferences from humidity and oxygen, at levels typically present in combustion environments [188], In this sensor, a steady-state potential arises when the oxidation-reduction reaction [186,188]... 

Mukundan. R., Teranishi, K., Brosha, E.L, and Garzon, F.H. (2007) Nitrogen oxide sensors based on yttria-stabilized zirconia electrolyte and oxide electrodes. Electrochem. Solid-State Lett., 10 (2), J26-9. 

Zhang, Y. et. al., A study of the process parameters for yttria-stabilized zirconia electrolyte films preparcd by screen-printing, J. Power Sources 160 (2006) 1065-1073. 

G. O. Lauvstad, R. Tunold, and S. Sunde. Electrochemical oxidation of CO on Pt and Ni point electrodes in contact with an yttria- stabilized zirconia electrolyte. J. Electrochem. Soc. 149, (2002) E497-E505. 

Figure 4.3.8. (a) Impedance response for a Pt/yttria-stabilized zirconia electrolyte with additives/Pt cell at 500°C and (b) the corresponding equivalent circuit. (Matsui [1981].)... 

Hibino T, Wang S, Kakimoto S, Sano M (1999) Single chamber solid oxide fuel cell constructed fiom an yttria-stabilized zirconia electrolyte. Electrochem Solid State Lett 2 317-319. doi 10.1149/1.1390822... 

Each of the three functional layers of the cell, anode, electrolyte, and cathode, are deposited onto the substrate using screen printing. In practice, each of the functional components requires multiple layers to provide the necessary functionality and manufacturability. Unlike other SOFC designs and similar to the metal-supported cell, the IP-SOFC uses neither the electrolyte nor electrodes to provide stmctural support. This allows very thin cells with consequently very small material quantities (cf. previous section). The cell functional layers again are made of conventional SOFC materials yttria-stabilized zirconia electrolyte, nickel cermet anode, and rare earth... 

Izzo et al. (2008) applied a high-resolution, nondestructive x-ray computed tomography (XGT) technique to image the three-dimensional microstructure of an SOFG composed of a solid yttria-stabilized zirconia electrolyte and a porous nickel YSZ anode. The x-ray microscope used the 8-keV Gu K line from a... 

Jiang, Z.Y., Zhang, L., Cai, L.L. Xia, C.R. Bismuth oxide-coated (La,Sr)Mn03 cathodes for intermediate temperature solid oxide fuel-cells with yttria-stabilized zirconia electrolytes. Electrochim. Acta 54 (2009c), pp. 3059-3065. 

W. Araki, Y. Imai, T. Adachi, Mechanical stress effect on oxygen ion mobility in 8 mol % yttria-stabilized zirconia electrolyte. J. Eur. Ceram. Soc. 29, 2275-2279 (2009)... 

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. 

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). 

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. 

Figure 29. Conductivity of some intermediate-temperature proton conductors, compared to the conductivity of Nafion and the oxide ion conductivity of YSZ (yttria-stabilized zirconia), the standard electrolyte materials for low- and high-temperature fuel cells, proton exchange membrane fuel cells (PEMFCs), and solid oxide fuel cells (SOFCs).

For the purposes of review. Figure 1 illustrates the basic function of the cathode in a solid oxide fuel cell. Whether acting alone or as part of a stack of cells, each cell consist of a free-standing or supported membrane of an oxygen-ion-conducting electrolyte, often yttria-stabilized zirconia (YSZ). Oxygen, which is fed (usually as air) to one side of the membrane, is reduced by the cathode to oxygen ions via the overall half-cell reaction... 

Solid oxide fuel cell (SOFC) working between 700 and 1000 °C with a solid oxide electrolyte, such as yttria-stabilized zirconia (Zr02-8% Y2O3), conducting by the... 

SOE cells utilize solid ceramic electrolytes (e.g. yttria stabilized zirconia) that are good oxygen ion (0 ) conductors at very high temperatures in the range of 1000°C [8]. The operating temperature is decided by the ionic conductivity of the electrolyte. The feed gas, steam mixed with hydrogen, is passed through the cathode compartment. At the cathode side, the reaction is... 

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