Single Crystal X-Ray Structure Analysis of Bi₂(Sr, Ca)₂CuO_x and Bi₂(Sr, Ca)₃Cu₂O_x Superconductors

Abstract

Average crystal structures of Bi 2 (Sr, Ca) 2 CuO x and Bi 2 (Sr, Ca) 3 Cu 2 O x were analyzed using single crystal X-ray intensity data applying anisotropic temperature factors. Crystal data: Bi 2 Sr 1.60 Ca 0.40 CuO 6 , Bbmb, a =5.3826(8) Å, b =5.3761(11), c =24.384(7), R w =0.108 for 282 reflections; Bi 2.06 Sr 1.70 Ca 1.24 Cu 2 O 8 , Bbmb, a =5.3946(8), b =5.3895(13), c =30.649(12), R w =0.064 for 354 reflections. Precession photographs show that Bi 2 Sr 1.60 Ca 0.40 CuO 6 has a monoclinic modulated structure and Bi 2.06 Sr 1.70 Ca 1.24 Cu 2 O 8 has an orthorombic one. The incommensurate modulated structures were qualitatively illustrated by using a modulation wave model.