Superconductors copper oxide

C. P. Poole, Jr., T. Datta, and H. A. Farach, Copper Oxide Superconductors, John Wiley Sons, New York, 1988. 

Influence of Valence, Electronegativity, Atomic Radii, and Crest-Trough Interaction with Phonons on the High-Temperature Copper Oxide Superconductors... 

In early 1987, the composition and structure of the La-Ba-Cu -O superconductor was still unknown to the general public in the United States. By March of that year certain facts became known from Japanese publications. But at this point in time, a newer, higher Tc (> 90 K) material was announced. This new copper oxide superconductor was quite easy to prepare and, in addition to interested physicists, these new materials could be synthesized by ceramists, chemists, metallurgists, material scientists, or anyone with a knowledge of a chemical approach to solid-state materials. Even high school students developed simple methods for the synthesis of these compounds. The "high" transition temperature and the possible use of liquid nitrogen made research in superconductivity accessible to most scientists and laboratories. The media also capitalized on this worthy news report and published it in newspapers and also presented it on television as a news item. 

Major Copper Oxide Superconductors Presently Being... 

The intent of this chapter is twofold. One is to give brief structural descriptions of many of the copper-oxide superconductors. For in-depth information, the reader is referred to the original publications. The second is to provide detailed crystallographic information (lattice constants, positional and thermal parameters, space groups, etc.), and compositional data on many of the superconductors discussed. Also, calculated x-ray powder diffraction patterns for these same compounds are tabulated. It is hoped that such information will prove useful to the superconductivity researcher. 

Poole, Jr., C., Datta, T. and Farach, H., Copper Oxide Superconductors, Wiley-Interscience, NY (1988). 

It is beyond the scope of this text to describe the mechanism for charge transfer in the high-temperature superconductors. While there is still a great deal of discussion on the applicability of BCS theory (cf. Section 6.1.1.3) to HTSC materials, it is safe to say that many of the principles still apply—for example, density of states at the Fermi level. The interested reader should refer to existing literature [3,4] for more information on the strucmre and theory of copper oxide superconductors. 

Cava, R.J. Structural Chemistry and the Local Charge Picture of Copper Oxide Superconductors, Science, 656 (February 9, 1990). 

Zhao G.-M., Hunt M.B., Keller H., and Mueller K.A., (1997). Evidence for polaronic supercarriers in the copper oxide superconductors La2 xSrlCu04. Nature 385 236-239. 

Table 1 Summary of the Known Copper-Oxide Superconductors...

L. Pauling, Influence of valence, electronegativity, atomic radii, and crest-tough interaction with phonons on the high-temperature copper-oxide superconductors. Phys. Rev. Lett. 59, 225-227 (1987). 

Copper oxide superconductor Bi2Sr2Cu06+z Bi203 4- 2SrO -F CuO 3 1110 ... 

All the copper oxide superconductors ever known contain a common structural unit the two-dimensional Q1O2 sheet... 

We have discussed the characteristics of a number of copper oxide superconductors, a group of materials that have many properties in common. These shared properties might well provide the key to the development of an explanation of the mechanism of high-temperature superconductivity. The most important common features are ... 

The one-meter-long conductor, based on a bismuth-strontium-calcium-copper oxide superconductor, carries over 2300 amps of direct current at liquid nitrogen temperatures (77 K). This is more than twice the current-carrying capability of conventional copper cables. 

Pale yellow cerium dioxide (ceria, ceric oxide) has the fluorite structure and is used in catalysis" ", solid oxide fuel cells (SOFC)", thin film optical waveguides" , reversible oxygen storage materials for automobile catalysts" and for doping copper oxide superconductors". The diverse cerium enolate precursors and deposition methods used in the formation of cerium oxide thin films are summarized in Table 6, whereby the most common precursor for ceria is Ce(thd)4. 

Magnetic flux pinning effect of impurities in copper oxide superconductors... 

With the use of the DV-Xa molecular orbital method, electronic structure calculations have been performed to investigate the impurity effect on material properties. Firstly, calculations were done for F atoms substituted for 0 (oxygen) atoms in copper oxide superconductors. It was found that the population of the atomic orbitals of F atoms is small in HOMO (highest occupied molecular orbital) and a small fraction of charge carriers enters the impurity sites. The F impurities are therefore expected to be effective for pinning magnetic flux lines in Cu oxide superconductors. 

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