Presentation Information
[WBP1-08]Comparison of Oxygen Annealing Effects on the Structure and Electronic State of YBCO 2G-HTS Tapes and Single-Phase Powders
*Maki Okube1, Kiyofumi Nitta2, Marat Gaifullin1, Roman Valikov1, Sergey Samoilenkov1, Valery Petrykin1, Sergey Lee1 (1. FFJ (Japan), 2. JASRI (Japan))
Keywords:
Electronic state,YBCO,PLD,Coated conductors
The superconducting performance of YBa2Cu3O6+x (YBCO) is governed by oxygen stoichiometry and carrier distribution in the CuO2 planes. While the relationship between lattice parameters and oxygen content is well established in bulk ceramics, fully oxidized YBCO thin films (HTS tapes) exhibit larger c-axis parameters than powders annealed under identical conditions. This raises the possibility that films retain lower oxygen content and could be further improved by optimized oxygen annealing, a key consideration for tailoring HTS wires for high-field use through strategies such as carrier overdoping and nanoscale pinning engineering to enhance Ic(B).
In this study, ceramic YBCO was synthesized by the Pechini method and compared with commercial YBCO 2G-HTS tapes fabricated by PLD. Both were subjected to identical oxygen annealing protocols, including high oxygen pressure, and their structural and electronic states were examined using X-ray absorption fine structure spectroscopy (XAFS).
Comparison of XAFS spectra for powders and tapes annealed under identical conditions reveals a striking distinction: in powders, fragments containing two-fold coordinated Cu atoms in O(apical)-Cu(chain)-O(apical) units disappear after annealing at 700℃, whereas these motifs persist in tapes even after full oxygenation, indicating hindered oxidation of the Cu-O chains. Meanwhile, the Cu and O electronic state in the CuO2 planes of tapes, as reflected in the hole concentration, is comparable to that of fully oxygenated powders. In other words, despite differences in lattice parameters, the electronic state of the Cu-O planes in tapes and powders is quite similar.
These findings indicate that the real structure of PLD-derived 2G-HTS films reflects an interplay among strain, oxygen ordering, and charge distribution, and ongoing analysis aims to clarify how PLD growth chemistry stabilizes this distinctive electronic state. They also provide new insights into optimizing the superconducting properties of 2G-HTS tapes for operation under extreme magnetic fields.
In this study, ceramic YBCO was synthesized by the Pechini method and compared with commercial YBCO 2G-HTS tapes fabricated by PLD. Both were subjected to identical oxygen annealing protocols, including high oxygen pressure, and their structural and electronic states were examined using X-ray absorption fine structure spectroscopy (XAFS).
Comparison of XAFS spectra for powders and tapes annealed under identical conditions reveals a striking distinction: in powders, fragments containing two-fold coordinated Cu atoms in O(apical)-Cu(chain)-O(apical) units disappear after annealing at 700℃, whereas these motifs persist in tapes even after full oxygenation, indicating hindered oxidation of the Cu-O chains. Meanwhile, the Cu and O electronic state in the CuO2 planes of tapes, as reflected in the hole concentration, is comparable to that of fully oxygenated powders. In other words, despite differences in lattice parameters, the electronic state of the Cu-O planes in tapes and powders is quite similar.
These findings indicate that the real structure of PLD-derived 2G-HTS films reflects an interplay among strain, oxygen ordering, and charge distribution, and ongoing analysis aims to clarify how PLD growth chemistry stabilizes this distinctive electronic state. They also provide new insights into optimizing the superconducting properties of 2G-HTS tapes for operation under extreme magnetic fields.