Effect of lithium doping on the properties of Tl-based superconductors

The effects of lithium doping on the formation and properties of the T1-bas ed superconductors have been studied. Lithium atoms up to around 3 mol.% ha ve been added to the oxides of nominal composition Tl1.8Ba2Ca2.2Cu3Ox, and the usual solid-state reaction method has been applied. Lithium additions i n the range 0.23-0.29 mol.% increase the fraction of the Tl-2223 phase and significantly improve the critical temperature of the samples. Higher amoun ts of lithium additions diminish the Tl-2223 phase, reduce the fraction of the Tl-2212 phase, and cause separate non-superconducting phases to be form ed.