Structural Study on High-T_c Superconductor Bi_<2-x>(Ca, Sr)_3Cu_<2+x>O_<9-y> : Electrical Properties of Condensed Matter

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The crystal structure of the high-T_c Bi_<2-x>(Ca, Sr)_3Cu_<2+x>O_<9-y> with x=0.2 and y=0.78 was studied by means of neutron and X-ray powder diffraction. Since the unit cell parameters were relatively large for powder diffraction analysis, an averaged structure was refined, assuming an orthorhombic sub-cell (a=5.39 A^^o, b=5.39 A^^o and c=30.37 A^^o) which corresponds to 1/5 of the unit cell: This is a derivative of Bi_4Ti_3O_<12>. The double perovskite unit interleaved by the double bismuth layers is B-type, i.e. a CuO_6 octahedron is surrounded by eight alkaline earth metal ions. The pyramidal Cuo_5 configuration is found in this oxide. The copper valency is estimated at about 2.3 on the basis of the determined chemical composition.
社団法人応用物理学会の論文
1988-04-20