Enhanced superconductivity by Mg doping in Cu1 − xTlxBa2Ca2 − yMgyCu0.5Zn2.5O10 − δ

We have enhanced the superconducting properties of newly discovered Cu0.5Tl0.5Ba2Ca2Cu0.5Zn2.5O10 − δ superconductor by doping Mg at Ca sites. The decreased c-axis length and the volume of the unit cell have shown that inter-ZnO2-plane coupling is enhanced. We have not observed any localization of the carriers in the neighbourhood of Zn atoms in Cu0.5Ba2Ca2 − yMgyCu0.5Zn2.5O10 − δ (y = 0, 0.5, 1.0, 1.5) superconductors, as proposed in the previous studies. The presence of Mg at the termination ends of the crystals has increased inter-grain coupling and substantially improved their weak link behaviour.