Yttria stabilized zirconias

Solid Oxide Fuel Cells Materials Properties and Performance 

When Y3+ cations are used to substitute Zr4 at the corresponding lattice sites, they also create vacancies in the oxygen sublattice since Y3+ cations have a lower valence than Zr4+. The vacancy production can be shown in Kroger-Vink notation similar to Equation 1.1. 

FIGURE 1.3 Conductivity of yttria- and scandia-stabilized zirconia in air at 1000°C. (Data from Fergus, J.W., J. Power Sources, 162, 30, 2006.) 

FIG U RE 1.4 Arrhenius plots for three Y203-Zr02 compositions showing different curvatures with increasing temperatures. (Data from Badwal, S.P.S., Solid State Ionics, 52, 23, 1992.) 

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TBCs consist of two different materials applied to the hot side of the component a bond coat applied to the surface of the part, and an insulating oxide applied over the bond coat. Characteristics of TBCs are that the insulation is porous, and they have two layers. The first layer is a bond coat of NICrAlY, and the second is a top coat of YTTRIA stabilized Zirconia. 

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). 

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.

T. Chao, K.J. Walsh, and P.S. Fedkiw, Cyclic voltammetric study of the electrochemical formation of platinum oxide in a Pt/yttria-stabilized zirconia cell, Solid State Ionics 47, 277-285 (1991). 

D. Kek, M. Mogensen, and S. Pejovnik, A Study of Metal (Ni, Pt, Au)/Yttria-Stabilized Zirconia Interface in Hydrogen Atmosphere at Elevated Temperature, J. Electrochem. Soc. 148(8), A878-A886 (2001). 

L. Basini, C.A. Cavalca, and G.L. Haller, Electrochemical Promotion of Oxygen Atom Back-Spillover from Yttria-Stabilized Zirconia onto a Porous Platinum Electrode Detection of SERS Signals,/. Phys. Chem. 98, 10853-10856 (1994). 

H.-D. Wiemhofer, and U. Vohrer, Spectroscopy and Thermodynamics of electrons in Yttria-stabilized Zirconia, Ber. Buns. Phys. Chem. 96, 1646-1652(1992). 

S. Wodiunig, F. Bokeloh, J. Nicole, and C. Comninellis, Electrochemical Promotion of R11O2 Catalyst Dispersed on an Yttria-Stabilized Zirconia Monolith, Electrochemical and Solid State Letters 2(6), 281-283 (1999). 

Yttria-stabilized zirconia by codeposition of tetramethyl heptadione of zirconium and yttrium, Zr(C Hi902)3 and Y(CnHi902)3 at 735°C. 

Attempts to deposit yttria-stabilized zirconia by combining Reaction (1) and a similar hydrolysis of YCI3 as source of yttrium at 700-1000°C were inconclusive, Codeposition from the chlorides... 

MOCVD of Zirconia. Yttria-stabilized zirconia is also deposited by MOCVD.Deposition can be accomplished by the codecomposition of the tetramethyl heptadiones of zirconium and yttrium, Zr(CjjHj902)3 and Y(CjjHj902)3, at 735°C. Deposition is also achieved by the decomposition of the trifluoro-acetylacetonates in a helium atmosphere above 300°C.P 1 Other potential MOCVD precursors are bis(cyclopentadienyl)zirconium dichloride, (C5H5)2ZrCl2, and zirconium (IV) trifluoroacetylacetonate,... 

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... 

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 parent structure of the anion-deficient fluorite structure phases is the cubic fluorite structure (Fig. 4.7). As in the case of the anion-excess fluorite-related phases, diffraction patterns from typical samples reveals that the defect structure is complex, and the true defect structure is still far from resolved for even the most studied materials. For example, in one of the best known of these, yttria-stabilized zirconia, early studies were interpreted as suggesting that the anions around vacancies were displaced along < 111 > to form local clusters, rather as in the Willis 2 2 2 cluster described in the previous section, Recently, the structure has been described in terms of anion modulation (Section 4.10). In addition, simulations indicate that oxygen vacancies prefer to be located as second nearest neighbors to Y3+ dopant ions, to form triangular clusters (Fig. 4.11). Note that these suggestions are not... 

Figure 4.11 Suggested defect cluster in yttria-stabilized zirconia. An oxygen vacancy is paired with two nearest-neighbor Y3+ ions. Relaxation of the ions in the cluster is ignored.

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).]... 

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],... 

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