Structural properties and cation ordering in layered hexagonal Ca{sub x}CoO{sub 2}
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100080 (China)
A series of Ca{sub x}CoO{sub 2} (0.15{<=}x{<=}0.40) materials have been prepared by means of an ion exchange reaction from Na{sub x}CoO{sub 2}. Transmission electron microscopy (TEM) measurements revealed a rich variety of structural phenomena resulting from cation ordering, structural distortion, and twinning. Systematic structural analysis, in combination with the experimental data of Na{sub x}CoO{sub 2} (0.15{<=}x{<=}0.8) and Sr{sub x}CoO{sub 2} (1.5{<=}x{<=}0.4) systems, suggests that there are two common well-defined cation ordered states corresponding, respectively, to the orthorhombic superstructure at around x=1/2 and the 3{sup 1/2}ax3{sup 1/2}a superstructure at around x=1/3 in this kind of system. Multiple ordered states, phase separation, and incommensurate structural modulations commonly appear in the materials with 0.33<x<0.5. The TEM observations also reveal an additional periodic structural distortion with q{sub 2}=a{sup *}/2 in materials for x{<=}0.35. This structural modulation also appears in the remarkable superconducting phase Na{sub 0.33}CoO{sub 2}{center_dot}1.3H{sub 2}O.
- OSTI ID:
- 20787815
- Journal Information:
- Physical Review. B, Condensed Matter and Materials Physics, Vol. 73, Issue 1; Other Information: DOI: 10.1103/PhysRevB.73.014109; (c) 2006 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 1098-0121
- Country of Publication:
- United States
- Language:
- English
Similar Records
Orthorhombic superstructures within the rare earth strontium-doped cobaltate perovskites: Ln{sub 1-x}Sr{sub x}CoO{sub 3-{delta}} (Ln=Y{sup 3+}, Dy{sup 3+}-Yb{sup 3+}; 0.750{<=}x{<=}0.875)
Searching for stable Na-ordered phases in single-crystal samples of {gamma}-Na{sub x}CoO{sub 2}