Yttrium barium copper oxide

About: Yttrium barium copper oxide is a research topic. Over the lifetime, 751 publications have been published within this topic receiving 6747 citations. The topic is also known as: YBCO.

High critical current density thick MOD-derived YBCO films

Abstract: High critical current density thick MOD (metal-organic-deposition)-derived Ba/sub 2/YCu/sub 3/O/sub 7-x/ (BYC) films have been prepared on latticed matched single crystal lanthanum aluminate substrates. Critical current densities of approximately one million amps per square centimeter (at 77 K) have been obtained from one micron thick BYC films. These superconducting films were prepared from a single MOD coating. Substrate coatings of a mixed metal trifluoroacetate precursor were first converted into high quality mixed metal oxyfluoride films by heat treating under controlled conditions. These films were then patterned and subsequently converted into epitaxial BYC by exposure to water vapor at higher temperatures, High critical current density films were obtained by controlling the conversion kinetics of the mixed metal oxyfluoride films into BYC.

Oxygen content of superconducting perovskites, lanthanum strontium copper oxide La2-xSrxCuOy and yttrium barium copper oxide YBa2Cu3Oy

Abstract: Studies of the composition of YBa/sub 2/Cu/sub 3/O/sub y/ in which the oxidation states of Y and Ba are +3 and +2, respectively, have shown a direct relationship between the Cu(II)/Cu(III) ratio and the oxygen stoichiometry. Idometry or hydrogen reduction has generally been used for the Cu(III) determination. A modification of the idometric method that is simple to apply and is particularly suited to analyses of La/sub 2-x/Sr/sub x/CuO/sub y/ and YBa/sub 2/Cu/sub 3/O/sub y/ is described. The results of application to determination of the oxygen content of YBa/sub 2/Cu/sub 3/O/sub y/ are presented, and the oxygen content is related to the crystallographic and superconducting properties of the material. Results indicated that at room-temperature large variations of the oxygen content of the orthorhombic phase of YBa/sub 2/Cu/sub 3/O/sub y/ could occur without change in the lattice parameters or appreciable impairment of the resistive superconducting transition or diamagnetic properties. 13 references, 1 figure, 1 table.

High-Performance YBCO-Coated Superconductor Wires

Abstract: This issue of MRS Bulletin provides an overview of the current status of research and development in the area of high-temperature superconductor (HTS) wires. High-temperature oxide superconductors, discovered in the late 1980s, are moving into the second generation of their development. The first generation relied on bismuth strontium calcium copper oxide, and the second generation is based on yttrium barium copper oxide, which has the potential to be less expensive and to perform better. The potential uses of HTS wires for electric power applications include underground transmission cables, oil-free transformers, superconducting magnetic-energy storage units, fault-current limiters, high-efficiency motors, and compact generators. Wires of 10-100 m in length can now be made, but material and processing issues must be solved before an optimized production scheme can be achieved. This issue covers a range of processing techniques using energetic beams, rolling, and laser and chemical methods to form wires with good superconducting properties.

Terahertz superconductor metamaterial

Abstract: We characterize the behavior of split ring resonators made up of high transition temperature yttrium barium copper oxide superconductor using terahertz time-domain spectroscopy measurements and numerical simulations. The superconductor metamaterial is found to show a remarkable change in the transmission spectra at the fundamental inductive-capacitive resonance as the temperature dips below the critical transition temperature. This resonance switching effect is normally absent in traditional metamaterials made up of regular metals. The temperature-dependent resonance behavior of the superconducting metamaterial would lead to development of low loss terahertz switches at cryogenic temperatures.

Variations of stoichiometry and cell symmetry in YBa2Cu3O7−x with temperature and oxygen pressure

Abstract: The mixed valence of copper (Cu(II)–Cu(III)) seems to be important in the recently discovered high-critical-temperature superconductivity of the yttrium barium copper oxide, YBa2Cu3O7−x; several authors have noted the influence of synthesis procedures on the superconducting critical temperature Tc (refs 1, 2). Recent structure determinations3–5 have shown the presence of oxygen vacancies, changing the copper coordination number from 6 in an ideal stoichiometric perovskite-type compound to 4 and 5 in YBa2Cu3O7−x. Here we report a thermogravimetric study of YBa2Cu3O7−x carried out at various temperatures and oxygen partial pressures, along with single-crystal X-ray diffraction data showing evidence of a crystallographic transformation as a function of temperature. The optimum copper valence is not reached under usual annealing conditions (800–1,000 °C), even in an oxygen atmosphere, but only below ∼350 °C. A change in the rate of oxygen loss with temperature may be related to an orthorhombic to tetragonal structural transformation occurring at ∼600 °C in air.