Oxides superconducting

Fig. 2.15. Comparison of the Cu 2p3 2 and satellite XPS spectra from several copper compounds with the spectrum from the superconducting oxide YBajCujOj [2.76],...

Fig. 2.16. TheSi2pand BaddXPS spectra [2.77] from (a) the clean surface of the superconducting oxide YBa2Cu307 (b)-(e) the same surface after increasing deposition of (b) 0.8 nm Si, (c) 2.8 nm Si, (d) 4.4 nm Si, (e)...

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... 

Reviews of superconducting oxides with emphasis on structures are ... 

In another research summary (10), this same point was driven home when the authors further indicated that NbO, TiO, and VO, the three most promising superconducting oxide candidates, were not observed to superconduct down to 1.20 K. By 1965, after much research, scientists were greatly astonished when the following results were finally obtained NbO, Tc = 1.38 K and TiO, Tc = 1.28 K. 

In Roberts report (3), a compilation of data to 1975 for over 3000 substances investigated as superconductors to different low temperatures, only 42 different oxide compositions are listed. These oxides can be classified into separate groups binary oxides =12 ternary oxides = 22 and multinary or complex oxides = 8. Of these, only 25 were found to superconduct and the highest superconducting transition temperature achieved in oxides was 2.3 K for nearly stoichiometric TiO. In 1978, Roberts presented (11) an addendum to his 1975 data set with the addition (or revision) of 8 new (mostly superconducting) oxides. 

TABLE 5 Milestones in Binary and Multinary Superconducting Oxides to 1975. 

Studies of Superconducting Oxides with the Sodium Chloride Structure... 

The superconductive oxides Pb2Sr2Ca1 xYxCu308 (36) and Pb2.xBixSr2Cai yYyCu308 (37) which exhibit a zero resistance at temperatures ranging from 46K to 79K respectively do not seem to... 

Within weeks after superconductivity was observed above 77 K in the Bi-Sr-Ca-Cu-O system, Sheng and Hermann (3) reported a record-high Tc value of 120 K for a Tl-Ba-Ca-Cu-O phase. The results were quickly confirmed (4)-(9) and the existence of a large family of thallium-containing superconducting oxides was revealed (10). 

Better control of the chemistry during synthesis should enhance resulting properties of the ceramics and the preparation of these superconducting oxides via solution techniques is therefore attractive. 

Balzarotti, A., Menushenkov, A.P., Motta, N. and Purans, J., EXAFS of the Superconducting Oxide BaPbj xBix03. Solid State Comm. 49(9) 887 (1984). 

Enomoto, Y., Murakami, T. and Suzuki, M., Infrared Optical Detector Using Superconducting Oxide Thin Film. Physica C 153-155 1592(1988). 

Electron Microscopy of High Temperature Superconducting Oxides... 

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