THE X-RAY STRUCTURE INVESTIGATIONS OF THE 4413 AND 2212 PHASES OF THE SINGLE CRYSTALS OF THE Bi_2O_3-SrO-CaO-CuO_(1+5)

摘要

The results of the X-ray goniometric development of the 2212 and 4413 phase single crystals of the Bi2O3-Sr0-Ca0-Cu0i+s system grown by the crucibleless zone heat technique are presented. It is found, in particular, that the studied phases are characterized by the pseudotetragonal crystal lattices complicated by the incommensurate modulations. The symmetry of the averaged structure is described by the A2aa or Amaa space group for 2212 [a=b=5.411(3)A, c=30.82(2)A] and Cm or C2/m space group for 4413 [a=5.413(3)A, b=5.413(3)A, c=27.72(2)A, p=90.00(5)°]. The structure modulation is characterized by the wave-vector q=0.21a*+c* for 2212 and 0.21a*+0.80c* for 4413.