元素置換を施した124型イットリウム系酸化物超伝導体の結晶構造

概要

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Crystal structures of YBa2Cu4O8 doped with Co, Fe, Ni and Ca are examined by nears of electron diffraction and high-resolution transmission electron microscopy (HRTEM) . Substitutions of Cu with Co and Fe result in an increase of planar defects due to replacement of (CuO) 2 double chain layers with (CuO) single ones. On the other hand, Ni-substitution has no significant effect on the 1-2-4 structure. As for the arrangement of (CuO) 2 double chain layers and (CuO) single ones, Co-substitution has a trend of ordered arrangements to form 2-4-7 or 3-6-11 structures at higher Co content, wheras Fe-substitution prefers a random one. In the Ca-doped specimens, three kinds of planar defects are observed: the planar defect due to the replacement of (CuO) 2 double chain layer with (CUO) single one, the 90° rotational twinning along the c-direction and the defect due to insertion of an additional Y (or Ca) layer between the two CuO layers of a (CuO) 2 double chain layer.
日本結晶学会の論文