Triclinic crystal structure of [(Bi1-xCox)2(Sr1-yBiy)2O4+δ]p[CoO2]2 with p∼1.05 and δ∼0.7

Bi-Sr-Co-O oxide semiconductor system has a typical misfit-layered crystal structure and a promising thermoelectric property. There are two different kinds of electron diffraction patterns taken with the electron beam parallel to the c-axis. Monoclinic unit cell was defined for the system having the metal ratio close to Bi:Sr:Co~1:1:1 by Leligny et al.¹⁾ The metal ratio of the present crystal is Bi:Sr:Co~1:0.8:1.1, being Co-rich and Sr-poor. The ratio was determined using an electron probe microanalyer. Oxygen content was determined by the inert gas-carrier fusion-infrared absorption method. Triclinic unit cell is determined by means of the whole pattern fitting technique, i.e., the Le Bail decomposition method, based on the neutron and X-ray power diffraction patterns, using a powder diffraction pattern fitting program Jana2000.²⁾ There are chemical content dependent changes in the structural parameters. The lattice parameters are typically a,b₁(RS),b₂(CoO₂),c,alpha,beta,gamma =4.94 Aring, 5.26 Aring, 5.45 Aring, 15.21 Aring, 90.2deg, 93.8deg, 89.3deg, respectively.