Oxygen stoichiometry and surface treatment effect on electromigration stability of high-T c Tl2Ba2CuO6+x superconductor

Electromigration stability of Tl₂Ba₂CuO_6+x ceramics is shown to decrease significantly when the material is treated in water vapor atmosphere. TheT _c decrease in these samples is accompanied by a resistance increase, while the Seebeck coefficient,S, remains unchanged. The authors conclude that the main effect comes from grain-boundary degradation under the water vapor treatment. For initial samples, electromigration stability strongly depends on the sample oxygen doping level and increases for materials with higher oxygen content. The effect is assumed to be due to the filling of interstitials in Tl-O layers by oxygen atoms.