Zirconia stabilization

Kavan, L. Attia, A. Lenzmann, F. Elder, S. H. Gratzel, M. 2000. Lithium insertion into zirconia-stabilized mesoscopic Ti02 (anatase). J. Electrochem. Soc. 147 2897-2902. 

FIGURE 1.10 Conductivity of zirconia stabilized with various dopants. 

The zirconia sensor operates primarily on the principle of a concentration cell. It consists of a non-porous solid electrolyte layer fabricated from zirconia stabilized with yttria or calcia and exhibits high oxygen ion mobility. This layer is sandwiched between two porous and electrically conductive electrodes. 

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... 

A gold-based material has been formulated for use as a three-way catalyst in gasoline and diesel applications.28 This catalyst, developed at Anglo American Research Laboratories in South Africa, consisted of 1% Au supported on zirconia-stabilized-Ce02, ZrC>2 and TiC>2, and contained 1% CoOx, 0.1% Rh, 2% ZnO, and 2% BaO as promoters. The catalytically active gold-cobalt oxide clusters were 40-140 nm in size. This catalyst was tested under conditions that simulated the exhaust gases of gasoline and diesel automobiles and survived 773 K for 157 h, with some deactivation (see Section 11.2.7). 

Zirconia (stabilized) ZrOj, 94% CaO, 4% 245 4800 Slightly acid Excellent 23 Low Excellent Excellent Very slight Very slight... 

Some dense inorganic membranes made of metals and metal oxides are oxygen specific. Notable ones include silver, zirconia stabilized by yttria or calcia, lead oxide, perovskite-type oxides and some mixed oxides such as yttria stabilized titania-zirconia. Their usage as a membrane reactor is profiled in Table 8.4 for a number of reactions decomposition of carbon dioxide to form carbon monoxide and oxygen, oxidation of ammonia to nitrogen and nitrous oxide, oxidation of methane to syngas and oxidative coupling of methane to form C2 hydrocarbons, and oxidation of other hydrocarbons such as ethylene, methanol, ethanol, propylene and butene. 

Zirconium oxide (ZrOfi. Is compatible with tungsten up to 1600 °C in vacuiun and up to 1400-1500 °C in protective atmospheres. Starting temperature indications in the literature are quite different due to differences in zirconia stabilization (2000-2390 °C). 

Zirconium dioxide, zirconia, is the only oxide of zirconium stable chemically at temperatures below 2000 K. At higher temperatures some dissociation into ZrO and oxygen takes place. The phases of ZrOj, their densities, and phase-transition temperatures are listed in Table 7.5. Zirconia stabilized in the high-temperature cubic phase by addition of 3 to S percent calcium oxide is used as a refractory at temperatures up to 2200° C. ZrOj has been used to dilute UOj in fuel elements. 

Ivaschenko O.V., Vasilev A.D., Peitchev V.G. et al. Fracture mechanisms, and strength of zirconia stabilized partially with yttria. Physical and chemical mechanics of materials, 1992, v.28, N6, p.46-50, in Russian. 

Other relevant property of such materials should be more sharp sensitivity to external influence of cubic zirconia stabilized by an impurity with smaller ionic radius (Sc ). Last statement guesses grater value of the effect of uphill diffusion in polycrystals Zr02 - 8 mol.% SC2O3 as contrasted to Zr02 - 8 mol.% Y2O3. However, measured value of mechanical-electrical effect for both materials within the framework of error of experiment has appeared practically identical that is the result of smallness of the found effect. 

Zirconia stabilized by yttria (3 mol. %) was used as initial nanopowder. It was produced from the salt containing hydro-cellulose fibers using the thermal treatment. During the treatment the solvent was removed and oxide fibers composed from nanograins of PSZ were formed. The fibers were grinded in fine dispersed powder from which half-finished products were formed. Some properties of the powder are presented in Table 1. 

Cubic stabilized zirconia stabilized usually with either CaO or Y2O3. 

Zirconia stabilized by calcia is an oxygen ion conducting solid electrolyte. The emf of the cell ... 

Early data with zirconia-stabilized ceria showed a major improvement over ceria by itself After aging at 1050 C, FTP testing showed sharp decreases in tailpipe concentrations of CO and NOx, together with smaller ceria particle sizes. This argued for effective structural stabilization. 

The Nextel 650 fiber is continuous and circular in cross-section with a diameter of 11.2 p,m and is composed of a-alumina and 10% wt of cubic zirconia stabilized by 1 %wt of... 

The Glass and Ceramics Institute of the Spanish CSIC carried out an analytical study of new materials used in structural and electrical ceramics, the stoichiometries and impurity contents of which were highly interesting because of their influence on the physico-chemical properties and service response of the pieces [24]. The specific materials studied were tetragonal zirconia stabilized with ceria and yttria (Y-TZP/Ce) lead titanate modified with gadolinium and doped with manganese (Gd-PT) and lead titanate-zirconate modified with lanthanum (PLZT). The first is a structural ceramic and the other two are electrical ceramics. 

The use of impedance spectra to determine the optimum electrode materials and preparation procedures for low-temperature oxygen sensors is only one example of the application of this technique in solid electrolyte sensors. For example impedance spectra have already been used to examine the properties of zirconia stabilizers such as yttria and calcia in low-temperature zirconia electrolyte oxygen sensors (Badwal [1983]). The use of this technique in the development and characterization of other solid state sensors should increase significantly in the next few years. 

Studies focusing on the use of sulfated zirconia have shown that reaction taking place at the strong acid sites also needs the metallic phase such as platinum for buming-off coke produced over sulfated zirconia, stabilizing the reaction intermediates of the isomerization. 

Molten salt method was previously applied for the synthesis of zirconia stabilized with yttrium and solid solutions were obtained [4]. The surface area of the product was found to be about 130 m /g, Such an yttria-stabilized zirconia was used as a catalytic support for hydrotreating catalysts. 

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