Dependence ofTcon hole concentration in the superconductors Bi4Sr3Ca3minus;xYxCu4O16+dgr;

摘要

Substitution of Y for Ca in the highTcsuperconductor system Bi4Sr3Ca3minus;xYxCu4O16+dgr;(0le;xle;1.5) is accompanied by an increase in oxygen concentration dgr;ape;0.34+0.3xthat is insufficient to compensate for the increase in counterhyphen;cation valence. Nevertheless,Tcape;86 K remains nearly constant in the interval 0le;xle;0.5; it drops smoothly to zero in the interval 0.5xle;1.15. Correlation of the compositional limitx=0.5 of theTcplateau with the onset of trapping of holes could indicate that any oxygen atom in excess of O16.5occupies a different crystallographic position where it traps two holes either as Bi5+or as (O2)2minus;.