Superconductivity in (Cu_(0.5)Tl_(0.25)Li_(0.25))Ba_2Ca_2Cu_(3-y)Si_yO_(10-δ) samples

摘要

The (Cu_(0.5)Tl_(0.25)Li_(0.25))Ba_2Ca_2Cu_(3-y)Si_yO_(10-δ)(y = 0, 0.25 0.5, 0.75, 1.0, 1.25) superconductor samples have been prepared by solid-state reaction method. The critical temperature and as well as the magnitude of diamagnetism is increased up to Si concentration y = 1.0, however, from the doping level y = 1.25 a decrease in the critical temperature along with the vanishing of the diamagnetism was observed. The carrier's in the conducting CuO_2/SiO_2 planes were optimized by carrying out post-annealing in oxygen and an increase in the critical temperature was observed in all Si doped samples. The doping efficiency of Cu_(0.5)Tl_(0.5)Ba_2O_(4-δ) charge reservoir layer in (Cu_(0.5)Tl_(0.25)Li_(0.25))Ba_2Ca_2Cu_(3-y)Si_yO_(10-δ)(y = 0, 0.25 0.5, 0.75, 1.0, 1.25) samples is enhanced by doping Li~(+1) ion; as alkali metals are known to easily loose their outer most electron which could be supplied to CuO_2/SiO_2 conducting planes and would suppress the anti-ferromagnetism in the inner conducting planes. The FTIR absorption measurements have provided an indirect evidence of Si substitution at in CuO_2 planes.