Materials Research | |
Study of the crystal structure of the high Tc superconductor Hg1-xRe xBa2Ca2Cu3O8+δ by using EXAFS, XANES and XRD | |
Luis Gallego Martinez2  Jesualdo Luiz Rossi2  Marcos Tadeu D'azeredo Orlando1  Carlos Augusto Cardoso Passos1  Hamilton Perez Soares Corrêa1  | |
[1] ,Nuclear and Energy Research Institute Materials Science and Technology Centre São Paulo SP ,Brazil | |
关键词: high Tc superconductor; XRD; EXAFS; XANES; Rietveld; | |
DOI : 10.1590/S1516-14392008000200004 | |
来源: SciELO | |
【 摘 要 】
Hg based superconducting ceramics present the highest critical temperatures ever reported, particularly the phase 1223 with the highest Tc so far obtained -135 K. However, these compounds are obtained by a complex synthesis route and suffer degradation at ambient atmosphere. This disadvantage may be overcome by doping with an appropriate amount of Re. Samples of nominal composition Hg0.82Re0.18Ba2Ca2Cu3O8+δ having different oxygen contents were studied by X ray absorption and diffraction techniques. Using XANES we determined the Re valence = +7 in an octahedral distorted coordination. We determined the distances of Re-O bonds (1.85 Å and 2.10 Å) by EXAFS. XRD Rietveld fits showed segregation of two superconducting phases with distinct lattice parameters. The main phase is associated with Hg, Re-1223 with higher oxygen content, and the secondary superconducting phase is related to undoped Hg-1223.
【 授权许可】
CC BY
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