CORRELATION OF STRUCTURE AND PROPERTIES IN Ba-DOPED Bi-2201 PHASE

In this article, it is revealed that the Ba substitution intensifies the incommens-urate modulation of the Bi-2201 phase, namely the wavelengths of the modulation along b and c directions show obvious decrease. The study of superconductivity of the Ba-doped 2201 shows that the appropriate substitution of Ba for Sr (x≤0.2) can raise the T c of 2201 phase, but as x exceeds 0.3, T c decreases sharply, simult-aneously accompanied with the superconductor-insulator. transition In addition, the characteristic feature of electronic structure of the Ba-doped 2201 phase is also stu-died by use of the XPS and UPS spectra. Based on all these experimental resuits, the relation between incommensurate modulation structure, electronic structure and superconductivity for the Bi-2201 phase are discussed comprehensively, indicating that the replacement of Ba ２＋ for Sr ２＋ intensifies the mismatch between Bi-O layers and perovskite blocks. and the enhancement of this mismatch influences the symme-try of Cu-O 2 planes seriously, just for this reason the variation of electronic state of Cu3d takes place (i.e. the degree of the coulomb correlation of the Cu3d electr-ons tends to be intensifled). In the process of Ba-doping, just due to the variation of Cu3d electrons, the 2201 phase undergoes a superconducting-insulating phase tran-sition.