Barium copper yttrium oxide

Yttrium—barium—copper oxide, YBa2Cu202 is a newly developed high T material which has been found to be fully superconductive at temperatures above 90 K, a temperature that can be maintained during practical operation. The foremost challenge is to be able to fabricate these materials into a flexible form to prepare wines, fibers, and bulk shapes. Ultrapure powders of yttrium—barium—copper oxide that are sinterable into single-phase superconducting... 

The acetylacetonates are stable in air and readily soluble in organic solvents. From this standpoint, they have the advantage over the alkyls and other alkoxides, which, with the exception of the iron alkoxides, are not as easily soluble. They can be readily synthesized in the laboratory. Many are used extensively as catalysts and are readily available. They are also used in CVD in the deposition of metals such as iridium, scandium and rhenium and of compounds, such as the yttrium-barium-copper oxide complexes, used as superconductors. 1 1 PI Commercially available acetyl-acetonates are shown in Table 4.2. 

The deposition of thin films of the high-temperature superconductor yttrium-barium-copper oxide, YBa2Cu307, is obtained from the mixed halides, typically YCI3, Bal2, and CUCI2, with O2 and H2O as oxygen sources. Deposition temperatures are 870-910°C.f ]... 

Kimura, Y., Ito, T., Yoshikawa, H., Tachiwaki, T., Hiraki, A. Growth and characterization of homogeneous yttrium-barium-copper-oxide (YBa2Cu307-delta) powders prepared by freezedrying method. Jpn. J. Appl. Phys., Part 2, 29 (8), L. 1409 - L 1411, 1990... 

Lacour, C., Laher-Lacour, F Dubon, A., Lagues, M., Mocaer, P. Freeze-drying preparation of yttrium barium copper oxide. Correlations between electrical and microstructural properties. PhysicaC (Amsterdam), 167 (3-4), p. 287-290, 1990... 

Yttrium—barium—copper oxide, 3 343, 369 Yttrium—barium—copper—oxide ceramics superconductivity in, 5 603-605 Yttrium distribution, in mineral sources, 14 637t... 

Yttrium-barium-copper oxide compounds YBa2Cu306+x (x = 0.6-1), generally abbreviated to 123, with a Tc of 90K which is above the temperature of liquid nitrogen, are of great importance (2). As noted earlier, Tc is governed principally by the crystal structure... 

A prototypical high-temperature superconductor is yttrium barium copper oxide, YBa2Cu307, in which two-thirds of the copper is in the +2 oxidation state and one-third is in the unusual +3 state. Another example is BijSrjlCaQgYoyjCujOgjys, in which the average oxidation state of copper is +2.105 and the average oxidation state of bismuth is +3.090 (which is formally a mixture of Bi3+ and Bi5+). The most reliable means to unravel these complex formulas is through wet oxidation-reduction titrations, described in this chapter. 

A breakthrough in superconductor technology came with the discovery24 of yttrium barium copper oxide, YBa2Cu307, whose crystal structure is shown here. When heated, the material readily loses oxygen atoms from the Cu-O chains, and any composition between YBa2Cu307 and YBa2Cu3Ob is observable. 

Ito, T., Kimura, Y., Hiraki, A. High-quality yttrium barium copper oxide (YBa2Cu3Oy x) ceramics prepared from... 

M. Schabel and Z.-X. Shen, Angle-resolved photoemission studies of untwinned yttrium barium copper oxide 391... 

London JE. 1988. Preliminary toxicological study of yttrium barium copper oxide. Carried out by Los Alamos National Laboratory, University of California. Washington, DC US Department of Energy, Office of Health and Energy Research. LA-11437-MS. 

B.D. Merkle, R.N. Knisely, FA. Schmidt, and l.E. Anderson, Superconducting Yttrium Barium Copper Oxide (YBa CUjO ) Particulate Produced By Total Consumption Burner Processing, Materials Science and Engineering, V01.A124, No.l, 1990, pp.31-38. 

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. 

Over the next few months, several experiments at Ar-gonne seemed to confirm that although superconducting currents flow through both chains and planes, the chains were the key structural feature that produced high-temperature superconductivity in the yttrium-barium-copper oxide. 

Electron micrograph of copper-oxygen planes in a sample of superconducting yttrium-barium-copper-oxide. Planes are well-defined up to the grain boundary. Photo courtesy of Argonne National Laboratory.)... 

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