The modulated structure of Bi2.49Sr2.00Co 2.22Ox is studied by electron diffraction analysis and high-resolution electron microscopy. The crystal structure consists of two interpenetrating subsystems of a CoO2 sheet and a distorted four-layered rock-salt-type (Bi,Sr)O block. Both subsystems have common a-axes, c-axes and β-angles with a = 4.99 Å, c = 15.25 A, and β = 93.6°. On the other hand, the crystal structure is incommensurately modulated parallel to the b-axis, in which b1 = 2.78 Å for the CoO2 sheet and b2 = 5.12 Å for the (Bi,Sr)O block, respectively. These vectors characterize the structural analogue as [Bi 2.08Sr1.67Oy]0.54[CoO2]. It is found that this compound has various modulation vectors, q1 = -a* + 0.54b1*, q2 = 0.05b1* and locally q3 = -0.14a* + 0.10b1*. The intrinsic modulation vector q2 is different from that in [Bi 0.87SrO2]2[CoO2]1.82 studied by Leligny et al. High-resolution images taken with the incident electron beam parallel to the a- and c-axes clearly exhibit modulated atomic arrangements. The local modulation mode characterized by the vector q 3 is associated with the shear deformation in the a-b plane.
|Number of pages||6|
|Journal||Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers|
|Issue number||5 A|
|Publication status||Published - May 9 2006|
All Science Journal Classification (ASJC) codes
- Physics and Astronomy(all)