Yttria-stabilized zirconia YSZ

Figure 4.3. Scanning electron micrographs of the top side of a porous Pt catalyst film (a) and of a section perpendicular to the Pt catalyst-yttria-stabilized zirconia (YSZ) interface (b).4 Reprinted with permission from Academic Press.

A hydrogen fuel cell is environmentally friendly, but H2 is much more difficult to store than liquid fuels. The production, distribution, and storage of hydrogen present major difficulties, so researchers are working on fuel cells that use liquid hydrocarbon fuels. One such fuel cell is composed of layers of yttria-stabilized zirconia (YSZ), which is solid Zr02 containing around 5% Y2 O3. This cell uses the combustion of a... 

FIGURE 1.2 Composition dependence of conductivity for yttria-stabilized zirconia (YSZ) measured at 1000°C [7], yttria-doped bismuth oxide (YDB) at 600°C [6], and yttria-doped ceria (YDC) at 700°C [8],... 

Y-section rayon, 11 262, 263 Ytterbium (Yb), 14 631t, 635t electronic configuration, l 474t Yttria, 5 583, 14 630 Yttria-stabilized zirconia (YSZ), 26 637 Yttric rare earths (RE), 14 631 Yttrium(III)... 

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. 

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... 

Screening tests were performed in a small laboratory-scale Alloy 625 autoclave (at 3,500 psi) charged with a small volume of liquid hydrolysate surrogate, a headspace of gas (oxygen or an inert gas), and coupons supported on yttria-stabilized zirconia (YSZ) buttons (for galvanic isolation from... 

An entirely different selectivity principle known as phase equilibrium comes into play in high-temperature ionic conductors. Many important gases dissolve in ionic solids at elevated temperatures. However, the solubility is rather sharply defined for the gas and the solid by the lattice parameters and the size of the gas molecule. The best example is the solubility of oxygen in zirconium dioxide. When Z1O2 is doped with yttrium ions, it exhibits a high mobility for the O anion. The solubility and anion mobility then become the basis for several electrochemical gas sensors, using yttria-stabilized zirconia (YSZ). 

Polycrystalline yttria-stabilized zirconia (YSZ-8) disks were prepared using 8 mol % Y203-doped zirconia powder (TOSOH zirconia, TZ-8Y, TOSOH Corp.). The powder was pressed uniaxially into disks which were cold isostatically pressed at 40,000 psi and then sintered at 1450°C for 4 h. Pt paste (Engelhard 6926) was painted on both faces of the YSZ-8 disks. Pt wires (0.0025 cm diam) were connected to the YSZ by using Pt meshes (150 X 150 mesh, 0.005 cm wire diam, Unique Wire Weaving Co., Inc.). 

A common type of oxygen sensor takes the form of an yttria stabilized zirconia (YSZ, see earlier) tube electroded on the inner and outer surfaces with a porous catalytic platinum electrode. The electrode allows rapid equilibrium to be established between the ambient, the electrode and the tube. Such a system is shown schematically in Fig. 4.36. 

Currently, the standard SOFCs use yttria-stabilized zirconia (YSZ) (see Section 2.4.3) containing typically 8 mol% of Y02 as the electrolyte, a ceramic metal (a cermet) composed of Ni plus YSZ as the anode, and lanthanum strontium manganite (LSM) perovskite (La Sr, MnO,, ) as the cathode material [5,7,9,135],... 

Zirconia, stabilized with 8-9 % yttria (yttria stabilized zirconia - YSZ) is the most commonly used electrolyte for SOFCs because it exhibits predominant ionic conductivity (O2- transport number close to unity) over a wide range of oxygen partial pressures (1 to 10 20 atmospheres). YSZ provides sufficient conductivity at... 

The electrical conductivity of rare-earth oxide fluorides was first investigated for the development of a binary anion conductive solid electrolyte. As a result, it was found that the binary rare-earth oxide fluorides exhibited oxide ion conductivity. Among them, the conductivity of neodymium europium oxide fluoride, Nd2Eu203F6, was reported to be much higher than that of yttria-stabilized zirconia, YSZ, practically used as an oxygen sensor [34]. The electrical conductivities of the binary rare-earth oxide fluorides vary not only with the combination of Ln203 with Ln F3... 

PEVD has been applied to deposit auxiliary phases (Na COj, NaNOj and Na SO ) for solid potenfiometric gaseous oxide (CO, NO, and SO ) sensors, as well as a yttria stabilized zirconia (YSZ) ceramic phase to form composite anodes for solid oxide fuel cells. In both cases, the theoretically ideal interfacial microstructures were realized. The performances of these solid state ionic devices improved significantly. Eurthermore, in order to set the foundation for future PEVD applications, a well-defined PEVD system has been studied both thermodynamically and kinetically, indicating that PEVD shows promise for a wide range of technological applications. 

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