CRYSTAL-STRUCTURE ANALYSIS OF CU0.6BA2CA3CU4O10.8 BY SINGLE-CRYSTAL X-RAY-DIFFRACTION METHOD

The small platelet single crystals of a new 116 K superconducting cupr ate having the structural formula Cu1-xBa2Ca3Cu4O12-y(x=0.4, y=1.2; Cu -1234) have been synthesized using a high-temperature and high-pressur e technique. This compound crystallizes in the tetragonal system, spac e group P4/mmm with a=3.8526(18) Angstrom and c=17.973(5) Angstrom. Th e crystal structure was determined from single-crystal X-ray diffracti on method and refined to the conventional values R=0.047 and wR=0.032 for unique 278 reflections collected up to 2 theta=70 degrees with Mo K alpha radiation. Some weak superlattice spots were also observed by the X-ray precession method. The crystal structure of Cu-1234 can be r egarded approximately as an intermediate between the infinite-layered structure and the Tl- or Hg-based 1234 structure. The existence of the deficient CuO2 sheet between two BaO layers in this compound, instead of a TlO2 sheet in the Tl-1234 structure, has been confirmed.