Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
1571132 | Materials Characterization | 2014 | 7 Pages |
Abstract
A series of compound with the nominal composition of Bi2Sr2 â xCaxCuO6 + δ (x = 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0) were synthesized by the sol-gel method. Constituent phases and crystal structure of samples were analyzed by X-ray diffraction. It can be found that the Ca-doped Bi-2201 system was composed of Bi-2201 phase containing Ca and a small quantity of Bi16(Sr,Ca)14O38. For Bi-2201 unit cell containing Ca, chemical component and site preference of Ca atoms were characterized systematically by transmission electron microscopy. With the introduction of Ca atoms, Sr-sites have been occupied partially by Ca2 + in Bi-2201 unit cell, which leads to a decrease in the lattice parameters c and b of the Bi-2201 phase when the Ca-content x is below 0.6. Two types of new orthorhombic lattices are formed in the substitution. One is a lattice with space group Pma2 as the two nearest neighbor Sr-sites in the same Sr-O layer are occupied by Ca2 +. Its lattice parameters can be characterized as a = 5.402 Ã
, b = 5.313 Ã
and c = 24.272 Ã
, respectively. When two nearest Sr ions of the second neighboring Sr-O layers are replaced by Ca2 + ions, the lattice with the space group Pmn21 can be formed. Its lattice parameters are close to that of the previous. The modulation vector is lying in the a*-c* plane in the two new orthorhombic lattices (Pma2 and Pmn21). Bi/Ca-2201 lattice (with Ca) and Bi-2201 lattice (without Ca) coexist in the same Bi2Sr2 â xCaxCuO6 + δ grain, which can be described as an intergrowth structure.
Related Topics
Physical Sciences and Engineering
Materials Science
Materials Science (General)
Authors
B.Z. Sun, S.L. Zhou, H. Wang, Z.Y. Fei, X.M. Lu, T.L. Wang, Y. Qi,