Abstract
Polycrystalline samples of RE0.6Ca0.4Ba1.6Sr0.4Cu3O6 (RE = Nd, Gd, Dy, Y, Yb, Lu) without oxygen in the Cu(1)O chain have been prepared by the conventional solid-state reaction method. No superconductivity appears for larger RE = Nd, Gd, Dy, while superconductivity with Tc ∼50 K appears for smaller RE = Y, Yb, Lu. This is presumably because holes produced by the Ca-substitution for RE are more supplied to the conductive Cu(2)O2 plane than to Cu(1) as the lattice becomes small. The maximum Tc = 53 K for RE = Lu is considerably lower than 90 K for REBa2Cu3O7. This may be due to the low hole-concentration in the Cu(2)O2 plane.
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