Zirconia yttria

Zirconia, yttria-stabilized, YSZ absolute potential of, 353 conductivity of, 93 nonstoichiometry of, 272 work function of, 353... 

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,... 

Doped zirconia, yttria and thoria Other oxides (magnesia, alumina, etc.) Electrolytic conductor Nonconductors... 

Electrolyte h3po4 Teflon (inert) Teflon (inert) Teflon (inert) Potassium hydroxide (KOH) Lithium carbonate / potassium carbonate or sodium carbonate Zirconia/ yttria Zinc oxide... 

Figure 7.8 Zirconia-yttria binary system. The introduction of yttria into zir-conia ( — 15-51% Y2O3) stabilizes the structure into the cubic form throughout the usable temperature range of the refractory material [11],...

Similarly, impervious yttria-stabilized zirconia membranes doped with titania have been prepared by the electrochemical vapor deposition method [Hazbun, 1988]. Zirconium, yttrium and titanium chlorides in vapor form react with oxygen on the heated surface of a porous support tube in a reaction chamber at 1,100 to 1,300 C under controlled conditions. Membranes with a thickness of 2 to 60 pm have been made this way. The dopant, titania, is added to increase electron How of the resultant membrane and can be tailored to achieve the desired balance between ionic and electronic conductivity. Brinkman and Burggraaf [1995] also used electrochemical vapor deposition to grow thin, dense layers of zirconia/yttria/terbia membranes on porous ceramic supports. Depending on the deposition temperature, the growth of the membrane layer is limited by the bulk electrochemical transport or pore diffusion. 

Scotford DM (1975) A test of aluminum in quartz as a geothermometer. Am Mineral 60 139-142 Scott HG (1975) Phase relationship in the zirconia-yttria system. J Mater Sci 10 1827-1835 Seifert F, Czank M, Simons B, Schmahl W (1987) A conunensurate-inconunensurate phase transition in iron-bearing ermanites. Phys Chem Minerals 14 26-35 Shannon RD (1976) Revised effective ionic radii and systematic studies of interatomic distances in halides and chalcogenides. Acta Crystallogr A32 751-767... 

H.W. Brinkman and A.J. Burggraaf, Ceramic membranes by electrochemical vapour deposition of zirconia-yttria-terbia layers on porous substrates. /. Electrochem. Soc., 142(11) (1995) 3851-3858. 

Caproni, E., Carvalho. F.M.S. and Muccillo, R. (2008) Development of zirconia-magnesia/zirconia—yttria composite solid electrolytes. Solid State Ionics, 179, 1652-4. 

Tsukuma, K., Ueda, K. and Shiomi, M. (1985) Mechanical properties of isostatically hot-pressed zirconia (yttria)/alumina composites. Proceeding of the 38th Annual Pacific Coast Regional Meeting of American Ceramic Society, Irvine, CA, October 1985. 

Figure 4.21. Part of the zirconia/yttria phase diagram that is of interest for the fabrication of partially stabilized zirconia. In the coexistence region some tetragonal phase is formed on cooling cubic zirconia doped with yttria. At still lower temperatures the tetragonal grains in the cubic matrix cannot convert to the monoclinic modification.

When a threshold stress is introduced into the creep equation, all of the creep parameters in YTZP become n=2, p = 2, and Q=460kjmol (the activation energy for cation lattice diffusion in a zirconia-yttria system [8]), whatever the stress or temperature of the test. Moreover, the data could be fitted to a constitutive equation which is identical to that found in metals, when the lattice diffusion is the ratecontrolling mechanism [62] ... 

A second example which illustrates the utility of IS to solid state chemists is the application of impedance analysis to zirconia-yttria solid electrolytes (Bauerle [1969]). At elevated temperatures solid solution zirconia-yttria compounds are known to be oxygen-ion conductors which function by transport of oxygen ions through vacancies introduced by the dopant yttria. By examining cells of the form... 

K. Kobayashi, H. Kayajima, and T. Masaki [1981] Phase Change and Mechanical Properties of Zirconia-Yttria Solid Electrolyte after Aging, Solid State Ionics 3/4, 489 93. 

In 1963, an important development was the zirconia membrane electrode showing ionic conductivity due to oxide ion (10). This electrode, initially composed of calcium oxide and zirconia, later has appeared in other forms, notably zirconia-yttria and zirconia-thoria. It has proven effective for oxide ion activity measurements over an extremely wide range at temperature of 1000 or higher, but it is of limited use at temperatures below 500 because of excessive resistance. 

By restricting attention to the complex dielectric constant, Volger concluded that in an N-layer MW situation, (N-1) relaxation times rather than N occur. As we have seen, this need not be the case. Bauerle used an N = 3 circuit to analyze data on zirconia-yttria by admittance plane methods. He found only two connected semicircles but omitted any parallel capacitance across one of his three resistances. This omitted capacitance can be identified as C to good approximation. Since there is always some geometric capacitance in any real situation, it should properly not have been omitted. At sufficiently high frequencies, it leads to a semicircle in the Z plane or a vertical line in the plane. Bauerle s data did not extent to high enough frequencies to show this effect. 

The assumption of unit activity for ZrO introduces only a very small error into the calculation as the zirconia-yttria fluorite solid solution only exhibits minor deviations from ideal behaviour. 

Jiang SP, Love JG, Zhang JP, Hoang M, Ramprakash Y, Hughes AE, Badwal SPS (1999) The electrochtan-ical performance of LSM/zirconia-yttria interface as a function of a-site stoichiometry and cathodic current treatment Sofid State Ionics 121 1-10... 

Biamino, S., Fino, P., Pavese, M. and Badini, C. (2005) Alumina-zirconia-yttria nanocomposites prepared by solution combustion synthesis. Ceramics International, 32, 509-13. 

There is a relation between material properties and morphology. In order to investigate this relation, Zhang et prepared nanorodlike, micro-spherical, micro-bowknot-like and micro-octahedral shaped ceria-zirconia-yttria (CZY) solid solutions vtith the surfactant-assisted hydrothermal method using a triblock copolymer (Pluronic P123) or cetyltrimethylammonium bromide (CTAB) surfactant. The formation mechanism of these materials by the surfactant-assisted hydrothermal method is shown schematically in Fig. 8.6. 

Figure 8.6 Formation of ceria-zirconia-yttria precursors and solid solutions under surfactant-assisted hydrothermal conditions. Reprinted with permission from Zhang et al Copyright 2009 the American Chemical Society.

Measurements of the conductivity of zirconia-calcia solutions [5,12,13,17—20] or zirconia-yttria solutions [20, 21] when plotted [22] as a function of the concentration of CaO or Y2O3 at 1000°C show a conductivity maximum between 10 and 15 % CaO or between 5 and 10% Y2O3 respectively. The maximum conductivity occurs close to the concentration of CaO or Y2O3 which is the lower limit for the cubic phase stabilization of zirconia. It is likely that the conductivity maximum is correlated to the number and distribution of vacancies. Plots of the logarithm of the resistivity versus 1/T at constant composition are linear for CaO contents between 12 and 15 % and for Y2O3 between 9 and 30% in the range between 800°C and 1400°C. Resistivities of about 25ficm... 

The yttria addition to the zirconia-yttria solid solution has two functions to stabilize the cubic structure type fluorite and to form oxygen vacancies in concentrations proportional to the yttria content. These vacancies are responsible for high ionic conductivity. Yttria stabilized zirconia is a suitable ionic conductor at temperatures above 800 °C, since thin dense membranes (less than 20 pm) can be manufactured. These membranes should be free of impurities. The stabilized zirconia is chemically inert to most reactive gases and electrode materials. 

Scott, H. G. (1975). Phase relationships in the zirconia-yttria system. Journal of Materials Science, 10, 1527-1535. doi 10.1007/BF01031853. 

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