EFFECT OF OXYGEN CONTENT ON THE CRYSTAL STRUCTURE AND SUPERCONDUCTIVITY IN Fe-DOPED YBCO SYSTEM

Abstract

The YBa 2 Cu 3-x Fe x O y(x=0, 0.1, 0.2) with different oxygen content has been studied through microstructure analysis and transport property measurements. The results show that the oxygen content has significant influence on the structure and superconductivity. Structure analysis shows that the microstructures of the YBCO system are dependent on the order of the Cu – O chains region. For Fe doped at Cu (1) site, the order of Cu – O chains have a close relation with the oxygen content y at low dopant concentration; when the dopant concentration is large enough (x≥0.2), the order of the chains could be destroyed, the structure becomes tetragonal and there seems to be no direct correlation with y. The suppression of superconducting transition temperature Tc caused by Cu (1) site substitution could be weakened by the increase in oxygen content to some extent. That is to say, Tc decreases with the decrease in y. The decrease in y not only makes the carrier density at the Cu – O chains region decrease but also forces the O (4) shifts to the Cu (1) site causing the enhancement of carrier localization at the Cu – O chains region which prevents charge transfer between the chains and planes, resulting in the decrease in Tc.