Enhanced Superconductivity in (Cu0.5Tl0.25Cs0.25)Ba2Ca2Cu3O10−δ by Cs Doping

The self doping of carriers in CuO₂ planes (accomplished through post annealing in air, N₂ and O₂ atmospheres in previous studies) is replaced by a more efficient alkali metal dopant such as Cs. The doping of Cs in the Cu_0.5Tl_0.5Ba₂O_4?δ charge reservoir of Cu_0.5Tl_0.5Ba₂Ca₂Cu₃O_10?δ superconductors has been found to enhance its superconducting properties. Enhanced superconductivity parameters, such as T _c, H _c and J _c, most likely arise from the enhanced doping efficiency of Cu_0.5Tl_0.25Cs_0.25Ba₂O_4?δ charge reservoir layer; since the alkali metals are known to lose their outermost “s-orbital” electron, which could be supplied to conducting CuO₂ planes. The distance between efficiently doped CuO₂ planes is reduced by Be and Mg doping at the Ca Sites. The quantity of diamagnetism and zero resistivity critical temperature T _c(R=0)] are suppressed by these substitutions. The post-annealing of the Cs doped samples further enhances their superconducting properties; oxygen doping most likely promotes the optimum holes concentration in the superconducting state in the Cs doped samples. These observations have also shown that the free carrier density plays a significant role in the mechanism of superconductivity which was accomplished by synthesizing (Cu_0.5Tl_0.25Cs_0.25)Ba₂Ca₂Cu₃O_10?δ superconductors.