Inter-grain connectivity in (Cu0.5Tl0.5−xHgx)Ba2Ca3Cu4O12−δ superconductor

Abstract

Abstract The connectivity of grains in (Cu 0.5 Tl 0.5− x Hg x )Ba 2 Ca 3 Cu 4 O 12− δ [Cu 0.5 Tl 0.5− x Hg x -1234] ( x = 0, 0.15, 0.25, 0.35) superconductors doped with Hg in the charge reservoir layer was studied. It was observed that inter-grain coupling is enhanced up to Hg doping level of 0.25 and weakened after Hg concentration of x = 0.35. The well-coupled grains have resulted in improved superconductivity parameters such as critical temperature ( T c ), peak temperature ( T p ), magnitude of diamagnetism and critical current ( I c ). We have found from these measurements that x = 0.25 is the critical doping level above which the superconductivity is suppressed. However, the post-annealing of the un-doped samples in oxygen has improved the superconducting properties, while nitrogen and air annealing has decreased the superconductivity. The critical current and the peak temperature T p of the x = 0.25 samples are decreased after post-annealing, which could be due to the change in intrinsic properties of the samples such as carrier concentration in CuO 2 planes.