Effect for Inhomogeneity by Pb Substitution on (Bi_1-yPb_y)₂Sr₂Ca_1-xY_xCu₂O_8+δSingle Crystals

S. Komaki, Y. Kourogi, T. Murano, A. Furushima, S. Maeda, Y. Sawada, B. Saya, Q. T. Meng, T. Tsuneoka, F. Ichikawa, K. Itoh

Department of Physics, Kumamoto University, Kumamoto, Japan..

DOI: 10.4236/msa.2012.312120                

Abstract

Inhomogeneity is one of the most important problems for the investigation of the superconductor-insulator transition. Y and Pb co-doped Bi₂Sr₂CaCu₂O_8+δ(PbY-Bi2212) crystals were fabricated by the self-flax method in order to control both carrier density and dimensionality. The Y-content of PbY-Bi2212 crystals was much wide distributed in the same crucible rather than that of only Y doping Bi2212 (Y-Bi2212) crystals. In order to clear the origin of inhomogeneity, crystals were characterized by wavelength-dispersive X-ray spectroscopy (WDS) and X-ray diffraction (XRD). One can estimate the Y-content of cleavage samples from the c-axis lattice parameter obtained by XRD because mainly Y-con- tent affects to c-axis lattice constant for both Y-Bi2212 and PbY-Bi2212 crystals. It found that there are some samples with multi-phases and the ratio of samples with multi-phase for PbY-Bi2212 crystals is larger than that for Y-Bi2212 crystals. The linear relation between Y-content and Pb-content were also found from WDS. Large inhomogeneity of Y-content may be induced from Pb-content inhomogeneity. Transport properties are strongly dependent to Y-content. However they cannot be explained only from the macroscopic chemical compositions of the substitution atom Y and Pb. It may be related to microscopic inhomogeneity.

Keywords

Superconductor-Insulator Transition; Inhomogeneity; XRD; WDS

Conflicts of Interest

The authors declare no conflicts of interest.

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