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Critical temperature of superconductivity and X‐ray crystallographic studies of Nb 0.78 Al 0.17 Ge 0.05 of A 15 structure
Author(s) -
Christensen K. N.,
Rasmussen S. E.,
Thygesen J.
Publication year - 1991
Publication title -
journal of applied crystallography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.429
H-Index - 162
ISSN - 1600-5767
DOI - 10.1107/s0021889890011104
Subject(s) - diffractometer , niobium , crystallography , powder diffraction , superconductivity , materials science , crystal structure , aluminium , single crystal , rietveld refinement , x ray crystallography , diffraction , transition temperature , analytical chemistry (journal) , chemistry , condensed matter physics , metallurgy , optics , physics , chromatography
Compounds of niobium and aluminium and of niobium, aluminium and germanium which crystallize in the A 15 structure were prepared by sintering and by floating‐zone methods. Single crystals of up to 1 × 1 × 1 mm were obtained for the composition Nb 0.78 Al 0.17 Ge 0.05 . Transition temperatures to superconductivity ranged from midpoint values of 18.6 to 19.4 K over intervals of 3 K. Single‐crystal X‐ray diffraction measurements were made at 293 and at 11–12 K. Powder diffractometer data were obtained at 293 K. The structure was refined with both powder data (Rietveld technique) and single‐crystal data. Photographic powder patterns were obtained from room temperature down to 11.7 K. No phase transition was observed. No evidence was found for deviations from the A 15 structure.