Oxygen concentration effect on Tc of the Bi-Ca-Sr-Cu-O superconductor
D. E. Morris, C. T. Hultgren, A. M. Markelz, J. Y. T. Wei, N. G. Asmar, J. H. Nickel
DOI 10.1103/PhysRevB.39.6612 · Physical Review B
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Abstract
The Tc of Bi2-Ca-Sr2-Cu2-O8−x can be shifted reversibly over a rangel of at least 15 K by changing the oxygen concentration. Tc shifts downward for increased oxygen content. This is opposite to the shift seen in YBa2Cu3O7−δ and may be caused by reduction in the Fermi level reducing conductivity in the Bi-O layers. Oxygen concentration is varied by treatment in O2 at appropriate pressures. The highest Tc=78.5 K of the ‘‘80-K’’ phase is obtained by treating at 600 °C in 10−2-bar oxygen. Tc shifts down to 65.4 K after treatment at 137 bars. The transitions remain sharp, with no evidence of significant structural change by x-ray powder diffraction. The original Tc is restored upon retreatment in O2 at low partial pressure. The 110-K phase showed a much smaller shift (ΔTc≊4 K) after treatment in O2 at 134 bar.
Source-reported materials — not catalogue approval
| Formula | Reported Tc (K) | Pressure (GPa) | Type |
|---|---|---|---|
| Bi2CaSr2Cu2O8-x Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 78.5 | Pressure not reported | onset |
| Bi2CaSr2Cu2O8-x Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 65.4 | Pressure not reported | onset |
| Bi2CaSr2Cu2O8-x Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 80 | Pressure not reported | onset |
| Bi2CaSr2Cu2O8-x Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 84.5 | Pressure not reported | onset |
| La2CuO4 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | — | Pressure not reported | unknown |
| YBa2Cu3O7-δ Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 92 | Pressure not reported | unknown |
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