Mironov Andrei V, Petříček Vaclav, Khasanova Nellie R, Antipov Evgeny V
Department of Chemistry, Moscow State University, Leninskie Gory, Moscow 119991, Russian Federation.
Institute of Physics, AVCR, Na Slovance 2, 182 21 Praha, Czech Republic.
Acta Crystallogr B Struct Sci Cryst Eng Mater. 2016 Jun 1;72(Pt 3):395-403. doi: 10.1107/S2052520616005643. Epub 2016 May 26.
The incommensurate modulated crystal structure of Bi2.27Sr1.73CuO6 + δ (2201) phase [a = 5.3874 (5), b = 5.3869 (4), c = 24.579 (3) Å; β = 90.01 (1)°, q = 0.2105 (3)a() + 0.538 (4)c(), Z = 4, the (3 + 1)-dimensional monoclinic A2/a(α0γ) 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, β2 = 93.06, q2 = 0.4524a2()-0.243c2() and the (3 + 1)-dimensional A2/m(α0γ)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 ∼ 0.6 Å from BiO towards the SrO layer. Its presence is the cause of the tremendous increase of the bismuth U(11) 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.
Bi2.27Sr1.73CuO6 + δ (2201) 相的非公度调制晶体结构 [a = 5.3874 (5), b = 5.3869 (4), c = 24.579 (3) Å；β = 90.01 (1)°, q = 0.2105 (3)a() + 0.538 (4)c(), Z = 4, (3 + 1) 维单斜 A2/a(α0γ) 群] 已根据包括高达三阶卫星反射的 X 射线单晶数据进行精修，R = 0.041，wR = 0.052。相同的结构也被视为具有 a2 = 2.437、b2 = 5.387、c2 = 24.614、β2 = 93.06、q2 = 0.4524a2()-0.243c2() 的非公度复合材料以及第二组分的 (3 + 1) 维 A2/m(α0γ)0s 群。两种方法给出的结果非常相似。该结构在 BiO 层的富氧区域存在氧无序。在从 BiO 向 SrO 层偏移约 0.6 Å 的桥接位置确定了一个额外的 O 原子。它的存在是约 20% 的晶胞中铋 U(11) 原子位移参数大幅增加的原因 (t = -0.05 - 0.15)。在 SrO 层的氧位点确定有空位，这可能导致在不同氧压力下退火时氧含量发生变化。精修后的总氧含量 6.18 (1) 与化学分析结果一致。
