材料期刊网

For Fe-doped Tl-1223 phase, the excess oxygen defects induced by Fe dopants are studied by means of Hall coefficient, thermogravimetric measurements, Mossbauer spectroscopy, and the model calculation of the effective bond valence. The extra oxygen defects have effects on carrier density and microstructure of the superconductors. In the light doping level of Fe (x=0-0.05), the superconducting transition and carrier density have significant corresponding relation- the zero resistance temperature T-co and carrier densities decrease linearly with Fe dopants increasing. The thermogravimetric measurements show that the Fe3+ ions' substituting for Cu2+ ions can bring the extra oxygen into the lattice to form extra oxygen defects. The calculation of the effective bond valence shows that the decrease of carrier density originates the strongly localized binding of the extra oxygen defects. The distortion of Cu-O layer induced by the extra oxygen defects decreases the superconductive transition temperature. The microstructures of the extra oxygen defects including the oxygen occupying and the shifts of Fe and O are discussed.