We have investigated the effect of the Sr-substitution for Ba on the superconductivity in Yb0.6Ca0.4Ba2- ySryCu3O6 without Ochain forming the so-called Cu(1)O chain in the blocking layer. It has been found that Tc increases with increasing y even though no holes are doped through the Sr2+-substitution for Ba2+. The increase in Tc is because holes doped by the Ca-substitution for Yb are more likely supplied to the superconducting Cu(2)O2 plane than the blocking layer of Cu(1) owing to the contraction of the Cu(2)O2 plane through the substitution of smaller Sr2+ for larger Ba2+. The highest Tc onset = 73 K observed for y(Sr) = 0.6 is greatly higher than the previous record of Tc onset = 50 K in (RE,Ca)Ba2Cu3O6 (RE: rare-earth element). The reason why it is lower than ∼90 K for REBa2Cu3O7 is the low hole-concentration in the Cu(2)O2 plane.
- Cuprate superconductor
- Elemental substitution
- Hole concentration
- RE-123 structure
- Superconducting transition temperature