Effect on Diamagnetism and Phonon Modes due to Mg and Be Doping at Ca Sites in Cu0.5Tl0.5Ba2Ca3-y M y Cu4O12-δ (y=0 and 1.5 for M=Mg, Be) High Temperature Superconductors

We synthesized as prepared and oxygen annealed Cu0.5Tl0.5Ba2Ca3-y M (y) Cu4O12-delta (y=0 and 1.5 for M=Mg, Be) High Temperature Superconductors (HTSCs) by using the solid state reaction method. It is observed that superconducting properties and the magnitude of the diamagnetism are enhanced by the doping of Mg and Be at the Ca site; this is due to smaller ionic sizes and higher electronegativities of Mg and Be as compared to Ca. Furthermore, interplanar coupling is also improved and shrinking of the axis length is the direct evidence of it. The carrier's concentration in conducting planes is improved by carrying out post-annealing experiments in the oxygen atmosphere. Moreover, FTIR absorption measurements are also incorporated.