New insight on bismuth cuprates with incommensurate modulated structuresстатья
Статья опубликована в высокорейтинговом журнале
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Дата последнего поиска статьи во внешних источниках: 18 июля 2016 г.
Аннотация:The incommensurate modulated crystal structure of Bi2.27Sr1.73CuO(6+delta) (2201)
phase [a = 5.3874 (5), b = 5.3869 (4), c = 24.579 (3) A ˚ ; beta = 90.01 (1), q =
0.2105 (3)a* + 0.538 (4)c*, Z = 4, the (3 + 1)-dimensional monoclinic A2/a(alpha,0,gamma)
group] has been refined with R = 0.041, wR = 0.052 from X-ray single-crystal
data including up to third-order satellite reflections. The same structure has also
been considered as incommensurate composite with a2 = 2.437, b2 = 5.387, c2 =
24.614, beta2 = 93.06, q2 = 0.4524a2*+0.243c2* and the (3 + 1)-dimensional
A2/m(alpha,0,gamma)0s group for the second component. Both approaches give quite
similar results. The structure possesses oxygen disorder in the oxygen-rich
region of the BiO layer. An extra O atom is determined in the bridging position
shifted about 0.6 A ˚ from BiO towards the SrO layer. Its presence is the cause of the
tremendous increase of the bismuth U11 atomic displacement parameter in
20% of the unit cells (t = -0.05 – +0.15). Vacancies are determined in the oxygen
site of the SrO layer, which may result in the oxygen content variation with
annealing at different oxygen pressures. The total refined oxygen content
6.18 (1) corresponds to the results of chemical analysis.