Superconductors copper oxide ceramic

The copper oxide ceramic superconductors are two-dimensional conductors They can conduct a current parallel to the layers of Cu and O atoms but not between the layers. The fullerides, by contrast, are three-dimensional conductors that conduct equally in all directions. Because of this property, they may prove to be superior materials for making superconducting wires. 

The theoretical interpretation of the high temperature superconductors is still under development. The copper oxide ceramic superconductors obtain their paired conducting electrons from copper in mixed oxidation states of I and II or II and III, depending on the particular system. The paired conducting electrons are called Cooper pairs, after Leon N. Cooper. Cooper s name also gives us the C of BCS the BCS theory is an interpretation of superconductivity for low temperature superconductors (having Tc s of less than 40 K). 

There are presently four famihes of high-temperature superconductors under investigation for practical magnet appheations. Table 11-25 shows that all HTS are copper oxide ceramics even though the oxygen content may vary. However, this variation generally has little effect on the phvsical properties of importance to superconductivity. 

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. 

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... 

A common feature of all the new ceramic superconductors is that they are cuprates, that is, they are complex copper oxides. The structure of YBCO is given in Fig. 19.3, which also shows that it is related to the perovskite structure (Fig. 4.17). Synthesis of YBCO is remarkably easy appropriate amounts of dry yttrium oxide (Y203), copper oxide (CuO), and barium carbonate (BaC03) are ground together into a fine, well-mixed... 

In 1986, the synthesis of copper-oxide based ceramics with a superconducting temperature (Tc) exceeding the boiling point of liquid nitrogen (77 K) was a major contribution in the scientific field. To date, a number of superconductors of this type have been prepared, and the highest Tc reached is 134K at... 

Something like that can go on in the new ceramic superconductors. In the yttrium-barium-copper oxide material, for example, if annealing—the heat treatment used to soften a material and make it more workable, and to relieve internal stresses and instabilities—goes on for too long, the ceramic begins to decompose if the annealing step is too short, it doesn t superconduct. 

Finally, in 1987 scientists discovered materials that became superconductors when cooled to only -183°C. These high-tem-perature superconductors were not metals but ceramics usually copper oxides combined with elements such as yttrium or barium. 

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