Superconducting properties of YBa2Cu3O7-Au composites

Abstract

By X-ray diffraction and photoelectron spectroscopy, we have demonstrated that Au is incorporated in the YBCO lattice up to a concentration 0.1. An XPS study gave evidence for an electronic valence state Au 1 +. Its replacement in the Cu(1 ) site appears questionable due to the large difference in ionic radii (Cu2+: 0.073 nm; Au 1+: 0.1 37 nm). The so called 'irreversibility lines' determined by AC susceptibility measurements are strongly affected by the doping. Up to the limit of solubility in the grains, an improvement in intra and intergrain coupling and flux pinning energy is observed, showing the beneficial interest of YBCO-Au composites.

The Dependence of the Flux Pinning Effects on the Au Mole Fraction in Y1Ba2Cu3-3xAu3xO7-? Superconductors

“…Figure 2 shows the zero-field-cooled (ZFC) and the field-cooled (FC) magnetization versus temperature characteristic curves of Y 1 Ba 2 Cu 3± ±3x Au 3x O 7± ±d for various Au mole fractions x = 0, 0.15, 0.1, 0.15, and 0.2. The critical temperatures of the superconductivity transitions for Y 1 Ba 2 Cu 3± ±3x Au 3x O 7± ±d are independent of the Au mole fraction, and the value of the T c is approximately 92 K. This behavior is in reasonable agreement with the results reported by Huong et al [16]. However, second transitions appear between 65 and 80 K and result from mixed phases being created in the Y 1 Ba 2 Cu 3± ±3x Au 3x O 7± ±d superconductors as the Au mole fraction increases.…”

Gold nanocrystals in high-temperature superconducting films: creation of pinning patterns of choice

“…Furthermore, it has been shown that Au has a certain solubility in YBCO so one could expect an efficient incorporation of gold atoms [35]. However, an incorporation of gold atoms should lead to an enhancement of the c-axis rather than to a thickness reduction as observed by the authors [36]. Furthermore, Rutherford backscattering spectrometry measurements proved that no gold atoms can be found at interstitial places.…”

Structural properties of gold modified YBa2Cu3O7−δthin films

“…Although this reduction of the c-axis in the gold modified sample parts is quite small, it is consistent over all the investigated samples. We do not expect a possible incorporation of gold atoms in the YBCO crystal structure to be responsible for this effect because it would only lead to an increase of the c-axis [13]. Instead we propose that a slight increase of the oxygen content might be causing the observed reduction of the YBCO c-axis [25].…”

“…The interplay of Au and YBCO has often been studied. In contrast to the existing work, which often was based on the usage of Au/YBCO composite targets [12] or grounded and sintered bulk pellets [13], we employ a self-organisation technique out of a gold seed layer. Thin gold layers with thicknesses between 1 and 10 nm were deposited on polished SrTiO 3 (100) single crystal substrates prior to the YBCO deposition using DC-sputtering (p 0 < 5 × 10 −4 Pa).…”