Superconductivity without dependence on valenceelectron density in Zn doped YBCO systems

This paper reports that the YBa_2Cu_3 - xZn_xO_7 - \delta \ (x=0-0.4) samples are researched by means of x-ray diffraction, calculations of binding energy, the positron experiments and variations of oxygen content. The results of simulated calculations, positron experiments and variations of oxygen content support the existence of cluster effect. Moreover, it is concluded that the cluster effect is an important factor on suppression of high-T_\rm c cuprate superconductivity and the T_\rm c does not depend on the density of valence electron directly.