Leonyuk L, Babonas GJ, Chernyshov V, Rybakov V, Maltsev V, Baran M
Moscow State University, Russia.
Acta Crystallogr A. 2000 Mar;56 (Pt 2):149-56. doi: 10.1107/s0108767399014889.
The structural regularities of (M2Cu2O3)m(CuO2)n-type (M = Ca, Sr, Y, Bi) cuprates with ladder-type planes have been considered. On the basis of the structural studies of the samples grown by floating-zone and flux methods, it was concluded that the phase (M2Cu2O3)(CU1+deltaO2+gamma), described as the m/n = 1/1 member, with Cu-deficient Cu-O ribbons in the series (M2Cu2O3)m(CuO2)n can be treated as an individual structural type intermediate between SrCu2O3 and incommensurate-type phases (M2Cu2O3)m(CuO2)n with m not equal n. The deficiency of the Cu sites in CuO ribbons is a particular crystal-chemistry feature of this structural type, in addition to the geometrical feature (m = n). The structural type of the 'Cu-deficient ladder' can transform into the incommensurate-type phases (M2Cu2O3)m(CUO2)n (m/n = 5/7, 7/10, 9/13 etc.) in the presence of free [CuO4]6- radicals in the melt. A realization of the (M2Cu2O3)m(CuO2)n phase with a particular m/n value is caused by the type of M cation. On the basis of recent data, the role of trivalent ions in the chemical composition of the (M2Cu2O3)m(CuO2)n-type compounds was also analyzed. The occurrence of the superconductivity in (Sr,Ca)CuO2 samples is discussed by analogy with cuprates of the infinite-layer structure.
研究了具有阶梯型平面的(M2Cu2O3)m(CuO2)n型（M = Ca、Sr、Y、Bi）铜酸盐的结构规律。基于对通过浮区法和助熔剂法生长的样品的结构研究，得出结论：被描述为m/n = 1/1成员的相(M2Cu2O3)(CU1+δO2+γ)，在系列(M2Cu2O3)m(CuO2)n中具有缺铜的Cu - O带，可以被视为介于SrCu2O3和m不等于n的非公度型相(M2Cu2O3)m(CuO2)n之间的一种独特结构类型。除了几何特征（m = n）外，CuO带中Cu位点的缺失是这种结构类型的一个特殊晶体化学特征。在熔体中存在游离的[CuO4]6-自由基时，“缺铜阶梯”的结构类型可以转变为非公度型相(M2Cu2O3)m(CUO2)n（m/n = 5/7、7/10、9/13等）。特定m/n值的(M2Cu2O3)m(CuO2)n相的实现是由M阳离子的类型引起的。基于最新数据，还分析了三价离子在(M2Cu2O3)m(CuO2)n型化合物化学成分中的作用。通过与无限层结构的铜酸盐类比，讨论了(Sr,Ca)CuO2样品中超导电性的出现。
