Local distortions of the Tl-O layers in Tl-based high-temperature superconductors
G. G. Li, J. Mustre de Leon, S. D. Conradson, M. V. Lovato, M. A. Subramanian
DOI 10.1103/PhysRevB.50.3356 · Physical Review B
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Abstract
Local distortions of Tl and O(3) atoms from the high-symmetry crystallographic sites in Tl2Ba2CuO6 and Tl2Ba2Ca2CuO8 have been observed by x-ray-absorption fine structure at the Tl LIII edge. The interlayer Tl-Tl distance around R=3.50 Å remains, but the intralayer Tl-Tl distance around R=3.87 Å is not found. The Tl-O(3) distances (in the Tl-O layers) are R=2.31 Å in Tl-2201 and R=2.35 Å in Tl-2212. These results show that both Tl and O atoms are shifted from their ideal crystallographic positions. The differences in the near-edge features of the x-ray-absorption spectra of these materials are consistent with this result. A negative edge shift of 1.2 eV at the Tl LIII edge compared to that of Tl2O3 indicates that the valence state of the Tl ion is less than 3+, which is consistent with charge-transfer models.
Source-reported materials — not catalogue approval
| Formula | Reported Tc (K) | Pressure (GPa) | Type |
|---|---|---|---|
| Tl2Ba2CuO6 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 89 | Pressure not reported | unknown |
| Tl2Ba2Ca2CuO8 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 105 | Pressure not reported | unknown |
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