UNIV SCI & TECHNOL BEIJING,DEPT MAT PHYS,BEIJING 100083,PEOPLES R CHINA
; CAS,INST HIGH ENERGY PHYS,BEIJING 100080,PEOPLES R CHINA
Article; Proceedings Paper
A excess oxygen model that explains the Fc-doping mechanism in 1223 Tl-Ba-Ca-Cu-O superconducting phasc is presented. So far the details of the coordination of Fc dopant is not understood completely yet, for Fe dopant substitution in Tl-system cuprate oxide. The similarity in the ionic radii and electronegativity of Ca and Fc lead to the Fc occupying Cu lattice site. However, the difference between the oxidation states of Fc and Cu means that Fc will bring the excess oxygen into lattice to keep the charge balance. We show that, for the evidence of the excess oxygen., the bonding energy of Fc-cluster in Cu-O layer reach its minimum when Fc make a shift from the center of Cu-O square network. Moreover, under the scheme of effective valence, the calculated value of Fc effective valence is relatively close to that of Mossbauer measurement.