Superconductor Ceramics

Electrical and Electronic Applications. Silver neodecanoate [62804-19-7] has been used in the preparation of a capacitor-end termination composition (110), lead and stannous neodecanoate have been used in circuit-board fabrication (111), and stannous neodecanoate has been used to form patterned semiconductive tin oxide films (112). The silver salt has also been used in the preparation of ceramic superconductors (113). Neodecanoate salts of barium, copper, yttrium, and europium have been used to prepare superconducting films and patterned thin-fHm superconductors. To prepare these materials, the metal salts are deposited on a substrate, then decomposed by heat to give the thin film (114—116) or by a focused beam (electron, ion, or laser) to give the patterned thin film (117,118). The resulting films exhibit superconductivity above Hquid nitrogen temperatures. 

As an example of the production of oxide systems, the ceramic superconductor YBa2Cu307 j has been prepared tlrrough the reaction... 

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... 

A unique application of the solid oxygen electrolytes is in dre preparation of mixed oxides from metal vapour deposits. For example, the ceramic superconductors described below, have been prepared from mixtures of the metal vapours in the appropriate proporhons which are deposited on the surface of a solid electrolyte. Oxygen is pumped tluough the electrolyte by the application of a polarizing potential across the electrolyte to provide the oxidant for the metallic layer which is formed. 

A unit cell of the mineral perovskite, which has a structure similar to that of some of the ceramic superconductors, is shown here. What is its formula ... 

CORROSION OF GLASS, CERAMICS AND CERAMIC SUPERCONDUCTORS edited by David E. Clark and Bruce K. Zoitos... 

This should come as no surprise, since the physical behavior of materials is non-linear and unpredictable, especially when materials are formulated or in combination. Two examples will suffice high temperature ceramic superconductors and insulators above their critical temperatures or at non-ideal stoichiometries composite structures may show several times the strength or impact resistance than would be expected from their component materials. Materials discovery will always require a good deal of trial and error, factors that may be mitigated by techniques that permit the simultaneous synthesis of large numbers of materials, followed by rapid or parallel screening for desired properties. 

The superconducting oxides include both perovskites and Ruddlesden-Popper compounds which have an orthorhombic arrangement of cubic cells, alternatively of the perovskite and sodium chloride structures. The common feature of all of these is the presence of copper as a major component. The first ceramic superconductor was a lanthanum-strontium substituted cuprate (Lai Sr Cu04 z), which is a perovskite, but subsequently the inter-oxide compound Y203 2BaO 3CuO, commonly referred to as a 123 compound, was shown to have superior performance. The speculation concerning the conduction mechanism is that this involves either Cu3+-Cu2+ positive hole... 

Figure 12 shows a number of geometric arrangements which are used in the construction of electrodes from ceramic superconductors. 

Another method used to study the reactivity of ceramic superconductors is to compare the cyclic voltammetric response of a reversible redox couple (in the present case [tcnq]0/ ) at a superconductor electrode with and without corrosion. As illustrated in Figure 14, in principle, in... 

Many different types of materials were later shown to exhibit aging and nonequilibrium dynamics, including polymers [91], orientational glasses [92], gels [93], and ceramic superconductors [94]. 

D.M. Smyth, Ceramic Superconductors n, Research Update. Publ. American Ceramic Society, Westerville, Ohio (1988). 

Many of the high Tc ceramic superconductors can be prepared by similar solid state techniques. In the Bi-Sr-Ca-Cu-O system Bi2Os, SrCOs, CaCOs or Ca(OH)2, and CuO are often used... 

One of the features first observed in BaPbj B Og, and now known as a hallmark of bulk ceramic superconductors is the appearance of grain boundary Josephson junctions. One of the most... 

Gilbert, L.R., Bulk and Sputtered Thin Film Ba(Pb,Bi)03 A Ceramic Superconductor. Ph.D. Thesis, Pennsylvania State U. (1979)... 

Ikegawa, S., Honda, T., Ikeda, H., Maeda, A., Takagi, H., Uchida, S-i., Uchinokura, K. and Tanaka, S., AC-DC Conversion Effect in Ceramic Superconductor BaPbj xBixOs. J. Appl. Phys. 64(10) 506l (1988). 

McGinnis, W., Jones, T., Jacobs, E., Boss, R. and Schindler, J., Critical Current Densities for the High Temperature Ceramic Superconductors Y-Ba-Cu-O and Bi-Sr-Ca-Cu-O. 1988 Applied Superconductivity Conference, San Francisco, CA (1988). 

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