Single Crystal X-Ray Structure Analysis of Bi2(Sr, Ca)2CuOx and Bi2(Sr, Ca)3Cu2Ox Superconductors

Abstract

Average crystal structures of Bi₂(Sr, Ca)₂CuO _x and Bi₂(Sr, Ca)₃Cu₂O _x were analyzed using single crystal X-ray intensity data applying anisotropic temperature factors. Crystal data: Bi₂Sr_1.60Ca_0.40CuO₆, Bbmb, a=5.3826(8) Å, b=5.3761(11), c=24.384(7), R _w=0.108 for 282 reflections; Bi_2.06Sr_1.70Ca_1.24Cu₂O₈, Bbmb, a=5.3946(8), b=5.3895(13), c=30.649(12), R _w=0.064 for 354 reflections. Precession photographs show that Bi₂Sr_1.60Ca_0.40CuO₆ has a monoclinic modulated structure and Bi_2.06Sr_1.70Ca_1.24Cu₂O₈ has an orthorombic one. The incommensurate modulated structures were qualitatively illustrated by using a modulation wave model.