Synthesis and properties of the 2:4:7 superconductors R2Ba4Cu7O15−x (R=Y,Eu,Gd,Dy,Ho,Er)
Donald E. Morris, Naggi G. Asmar, John Y. T. Wei, Janice H. Nickel, Randy L. Sid, Jeffrey S. Scott, Jeffrey E. Post
DOI 10.1103/PhysRevB.40.11406 · Physical Review B
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Abstract
Six high-temperature superconducting compounds R2Ba4Cu7O15−x (R=Y,Eu,Gd,Dy,Ho,Er) are synthesized in oxygen at moderate pressures above 1 bar. Each 2:4:7 compound is stable only within a narrow range of oxygen pressures bounded by the stability regions of the 1:2:4 and 1:2:3 phases; the required P(O2) varies with temperature and R-ion radius. Our 2:4:7 compounds show low Tc’s (45–55 K) which vary inversely with ion size (as in 1:2:4). The basal plane areas are larger and orthorhombic distortions smaller than the corresponding 1:2:3 and 1:2:4, suggesting smaller oxygen content, lower hole concentration and weaker bonding in the CuO2 layers. The 2:4:7 phase has variable oxygen stoichiometry, and Tc decreases when oxygen is removed.
Source-reported materials — not catalogue approval
| Formula | Reported Tc (K) | Pressure (GPa) | Type |
|---|---|---|---|
| Eu2Ba4Cu7O15-x Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 45 | Pressure not reported | onset |
| Gd2Ba4Cu7O15-x Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 45 | Pressure not reported | onset |
| Dy2Ba4Cu7O15-x Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 50 | Pressure not reported | onset |
| Y2Ba4Cu7O15-x Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 55 | Pressure not reported | onset |
| Ho2Ba4Cu7O15-x Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 55 | Pressure not reported | onset |
| Er2Ba4Cu7O15-x Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 55 | Pressure not reported | onset |
| Yb2Ba4Cu7O15-x Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 86 | Pressure not reported | unknown |
| YBa2Cu3O7 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 92 | Pressure not reported | unknown |
| YBa2Cu4O8 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 81 | Pressure not reported | unknown |
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