Solid ceramic oxide electrolyte

Solid Oxide Fuel Cell In SOF(7s the electrolyte is a ceramic oxide ion conductor, such as vttriurn-doped zirconium oxide. The conduetKity of this material is 0.1 S/ern at 1273 K (1832°F) it decreases to 0.01 S/ern at 1073 K (1472°F), and by another order of magnitude at 773 K (932°F). Because the resistive losses need to be kept below about 50 rn, the operating temperature of the... 

In the ceramics field many of the new advanced ceramic oxides have a specially prepared mixture of cations which determines the crystal structure, through the relative sizes of the cations and oxygen ions, and the physical properties through the choice of cations and tlreh oxidation states. These include, for example, solid electrolytes and electrodes for sensors and fuel cells, fenites and garnets for magnetic systems, zirconates and titanates for piezoelectric materials, as well as ceramic superconductors and a number of other substances... 

It is to be expected that the conduction data for ceramic oxides would follow the same trends as those found in semiconductors, i.e. the more ionic the metal-oxygen bond, the more the oxides behave like insulators or solid electrolytes having a large band gap between the valence electrons and holes, and... 

Ionic conductors, used in electrochemical cells and batteries (Chapter 6), have high point defect populations. Slabs of solid ceramic electrolytes in fuel cells, for instance, often operate under conditions in which one side of the electrolyte is held in oxidizing conditions and the other side in reducing conditions. A signihcant change in the point defect population over the ceramic can be anticipated in these conditions, which may cause the electrolyte to bow or fracture. 

Kharton VV, Marques FMB, Atkinson A (2004) Transport properties of solid oxide electrolyte ceramics a brief review. Solid State Ionics 174 135-149... 

Solid oxide (SOFC). The electrolyte is a ceramic oxide and operates at 1000°C and can consume hydrogen or hydrogen/carbon monoxide mixtures. A high electrical efficiency of over 50 per cent is reported. 

Mobius H and Roland B, 1968, Method of Producing Fuel Cells with Solid Electrolytes and Ceramic Oxide Electrode Layers. US Patent 3,377,203. 

Badwal, S.P.S. and Foger, K., Solid oxide electrolyte fuel cell review. Ceramics International, 1996, 22, 257-265. 

N. Q. Minh, J. Am. Ceram. Soc., 76, 563 (1993). Excellent review of the solid oxide fuel cell including a thorough treatment of the ceramic components (electrolyte, anode, cathode, and interconnect). 

Solid oxide fuel cell (SOFC) uses solid ceramic material, such as Y2O3 stabilized Zr02 (YSZ), as an electrolyte. As SOFC operates at high temperature (600-1000° C), a variety of fuels, e.g., hydrogen, methane, and carbon monoxide, can directly be utilized. The high temperature places severe constraints on material selection and results in difficult fabrication process. Co-ZrO (or Ni-ZrO) and SrO doped LaMn03 have often been used for anode and cathode materials, respectively. 

FIGURE 1.13 1 Low boundary of the oxygen-ionic conductivity for the solid (Zr02)o.9(Y203)o 1 electrolyte and 2 and the temperature dependence of logarithm pressure of dissociation for oxide Na20. (From Zhuiykov, S., Electron model of solid oxygen-ionic electrolytes used in gas sensors, Int. J. Applied Ceramic Techn. 3 (2006) 401-411. With permission.)... 

Key words Sealant/Glass-Ceramics/Thermal Expansion/Solid Oxide Electrolyte/Transport Properties... 

Trunec has described the thermoplastic extrusion of thin-wall tubes made of yttria-stabilized zirconia and gadolinia-doped ceria [Tru 04], These ceramics are used for solid oxide electrolyte applications, e.g. solid oxide fuel cells. The thermoplastic binder system used consists of ethylene-vinyl acetate copolymer, parafHn wax and stearic acid. With this system tubes with an outer diameter of 10.5 mm and wall thicknesses of 290 and 280 pm could be fabricated. 

High-temperature electrolysis using a solid oxide electrolyte the ceramic ion conductor also separates the electrode chambers. 

In a SOEC, the membrane is an oxygen ion-conducting electrolyte. It is a solid ceramic which allows migration of oxide ions. The most common electrolyte used is YSZ, because of its high oxide ion conductivity and its good mechanical strength. As for SOFC apphcations, the membrane has to be dense and chemically stable. Moreover, the best conversion efficiency is obtained when the electrolyte has a high ionic conductivity. To minimise ohmic loss, the membrane has to be as thin as possible (Ni et a/., 2008). 

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