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Dependence of T c on the Hole Concentration in the High‐ T c Superconductors Bi 1.5 Pb 0.5 Sr 2 Ca 1− x Gd x Cu 2 O 8+ z
Author(s) -
Kiemel R.,
Wischert W.,
KemmlerSack S.
Publication year - 1989
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.2221560134
Subject(s) - superconductivity , condensed matter physics , percolation (cognitive psychology) , superconducting transition temperature , electrical resistivity and conductivity , transition temperature , materials science , analytical chemistry (journal) , physics , metal , chemistry , chromatography , quantum mechanics , neuroscience , metallurgy , biology
Substitution of Gd for Ca in the high‐ T c superconductor Bi 1.5 Pb 0.5 Sr 2 Ca 1− x Gd x Cu 2 O 8+ z (0 ≦ x ≦ 1.0) is accompanied by a decrease in hole concentration with increasing x . Nevertheless, T c ≈ 90 K remains nearly constant in the interval 0 ≦ x ≦ 0.25. Compounds with x = 0.35 and 0.5 are still superconducting; the increased width of the transition points on a percolation of superconductivity. Compounds with x ≧ 0.75 are semiconductors. The presence of variable range hopping in the insulating regime strongly suggests that the metal—insulator transition is of Anderson type.