OXYGEN STOICHIOMETRY AND SURFACE-TREATMENT EFFECT ON ELECTROMIGRATIONSTABILITY OF HIGH-T-C TL2BA2CUO6+X SUPERCONDUCTOR

Electromigration stability of Tl2Ba2CuO6+x ceramics is shown to decrea se significantly when the material is treated in water vapor atmospher e. The T-c decrease in these samples is accompanied by a resistance in crease, while the Seebeck coefficient, S, remains unchanged, The autho rs conclude that the main effect comes from grain-boundary degradation under the water vapor treatment. For initial samples, electromigratio n stability strongly depends on the sample oxygen doping level and inc reases for materials with higher oxygen content. The effect is assumed to be due to the filling of interstitials in Tl-O layers by oxygen at oms.