Properties of boron doped Tl-Ba-Ca-Cu-O superconductors

The effects of boron doping on the formation and properties of the Tl-based superconductors have been studied. Up to 10 wt.% boron has been added to the oxides having the nominal composition, Tl_1.8Ba₂Ca_2.2Cu₃O_x, by the usual solid-state reaction method. Boron additions in the range 0.8-1.0% increase the fraction of the Tl-2223 phase and significantly improve the critical temperature of the samples. Higher amounts of boron additions eliminate the Tl-2223 phase, reduce the fraction of Tl-2212 phase and cause separate non-superconducting phases to be formed. The formation of non-superconducting phases does not allow us to obtain pure Tl-2212 phase.