STRUCTURE AND PROPERTY OF Y-Ba-Cu-Sn-O SYSTEM

摘要

By comprehensively determining the lattice parameter, XPS, Mssbauer spectrum, relationship between the resistance and the temperature, oxygen content and the thermal decomposition temperature of the samples of YBa₂Cu_3-xSn_xO_7+y system, it is discovered that Sn occupies the site of Cuin the form of Sn4+ oxidation state. The change of crystalline structure as well as T_c are very little for x0.4. The oxygen content of the samples is increased by the substitution of Sn for Cu, which influences the valence of Cu obviously, and makes the Cu be in the Cu3+ state. The experimental results give some important information on understanding the origin of superconductivity from the structure, oxygen deficiency, and electronic state. From analysis, it is suggested that the coupling strength between metals and oxygen determines the superconductivity.