Superconductivity Without Relation to Valence Electrons in (Fe, Zn) Doped YBCO Systems

Abstract

We systematically investigated YBa2Cu3−x(Fe, Zn)xO7−δ (x=0.0∼0.5) cuprates through XRD, the test of superconductivity, oxygen contents, positron annihilation technology and simulated calculations. With the Fe and Zn doped concentration increasing, the transition temperature Tc drops from 92 K for the undoped YBa2Cu3O7−δ. The form of the Fe or Zn ion cluster in both doping samples illuminates the variation of the oxygen content. The experimental results and theoretic calculations support such a conclusion that the transition temperature Tc does not depend directly on the density ne of the valence electron in the samples.