The Role of Oxygen Content in YBa₂Cu₃O_y Superconductors

Based on the EHMO approach,an approximate band-structure treatment,which can be employed to investigate the effects of random vacancies, was suggested. By use of this treatment, the electronic structures of YBa₂Cu₃O_y（6≤y≤7） were calculated and the role of the oxygen content in the Y-Ba-Cu-O superconductors was studied. The result show that as the oxygen content y deceases,the band structures for YBa₂Cu₃O_y are greatly changed at y≈6. 5 and their electronic densities of states are de-craesed rapidly. In addition, the role of structural fractions of crystals in the electronic structures was also investigated and it is concluded that the 2D Cu-O planes play a dominant role in the Y-Ba-Cu-O superconducting systems.