DOPING EFFECTS IN YBa 2 Cu 1-x Co x (Cu 1-y Zn y ) 2 O z SYSTEM

The crystal structure, oxygen content, resistance, Hall effect and superconducting crkical temperature of YBa 2 Cu 1-x Co x (Cu 1-y Zn y ) 2 O z system (0≤x, y≤0.1) have been studied. It is found that with increase of Co and Zn contents, the transformation from superconducting metal with orthorhombic structure to non-superconducting semiconductor with tetragonal structure occurs. At the same time, the T c and the carrier density n h decrease sharply. The effects with Co and Zn doping simultaneously are not simply additive. With increase of Co and Zn concentrations, there is a strong coorelation between Co doping on Cu(l) and Zn on Cu (2) sites. The experimental results show that the coupling between Cu-O planes and Cu-O chains gives much influence on the electronic transport properties in normal states and superconductivity. The characteristics of the hole carriers and its dependence on T c in 123 phase compounds are also dicussed.