Correlation between electronic states of oxygen and copper in YBaCuO doped systems

Abstract

The electronic states of copper and oxygen in YBaCuO and five doped systems (Ba is doped by Sr, Ca;Cu by Zn, Al, Sn, respectively) are studied by XPS, the oxygen contents of samples are determined by thermogravimetric analysis. The experimental results show that there is strong correlation between the electronic states of copper and oxygen. The samples, in which the difference of two states of O 1s is indistinct and the oxygen content high, show partial Cu 3+ oxidation state. In contrast, the samples, in which the difference of two states of O 1s is clear and the oxygen content low, show entire Cu 2+ oxidation state. Comparing these results with the superconductivity of samples, it is found that Cu 3+ state has no direct relationship with superconductivity. The experimental results demonstrate that Cu 3+ state is only the result of the charge balance in the systems.