Role of bromine in restoring superconductivity in YBa2Cu3Oy
D. M. Potrepka, J. I. Budnick, D. B. Fenner, W. A. Hines, M. Balasubramanian, A. R. Moodenbaugh
DOI 10.1103/PhysRevB.60.10489 · Physical Review B
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Abstract
63,65Cu nuclear quadrupole resonance (NQR), 63,65Cu and 79,81Br nuclear magnetic resonance (NMR), and Br K-edge x-ray-absorption fine-structure (XAFS) measurement techniques have been used to study the local structures of Cu and Br in well-characterized samples of deoxygenated and brominated YBa2Cu3Oy (YBCO). The combined results provide a detailed picture of the role of bromine in reoxygenating the YBCO structure and an explanation for the partial restoration of superconductivity in the YBCO system. Characterization of the powder samples, with particle sizes of 1, 20, 30, and 40 μm, included x-ray diffraction, thermal gravimetric analysis, energy dispersive x-ray analysis, and magnetometry. From the XAFS and NMR results, it is concluded that, upon bromination at 260 °C, Br does not enter the YBCO lattice either substitutionally or interstitially. Instead, there is compelling evidence for the formation of nanoscale BaBr2 precipitates which result from the local destruction of the YBa2Cu3Oy phase. Furthermore, on the basis of the NQR and NMR experiments, it is concluded that through this decomposition into an inhomogeneous material, oxygen is liberated which repopulates the nearby O(4) chain sites, thus restoring superconductivity.
Source-reported materials — not catalogue approval
| Formula | Reported Tc (K) | Pressure (GPa) | Type |
|---|---|---|---|
| YBa2Cu3O6.9 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 86 | Pressure not reported | unknown |
| YBa2Cu3O6.6 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 48 | Pressure not reported | unknown |
| YBa2Cu3O6.1 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | — | Pressure not reported | unknown |
| YBa2Cu3O6.2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | — | Pressure not reported | unknown |
| YBa2Cu3O6.7 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 58 | Pressure not reported | unknown |
| YBa2Cu3O6 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | — | Pressure not reported | unknown |
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