Location of fluorine atoms and mechanism of improving superconducting properties with F-doped in YBaCuO series

摘要

A series of YBa 2Cu 3O 6.5-0.5x+δ F x (x=0, 0.3, 0.6, 1.0, 1.5, 2.0) samples were synthesized using state reaction method. The superconducting properties and microstructures of the samples were studied with AC susceptibility, DC resistivity, fluorine and oxygen content measurements, XRD, IR and XPS techniques. The results show that F doping increases the T C and decreases the transition width, and fluorine atoms have entered into the superconducting phase and substituted for the oxygen atoms at O(4) sites. The mechanism of improving superconducting properties is that fluorine doping adjusts the hole carrier concentration in the Cu O planes.