Oxides of the LnBaCaFeO (Ln = Gd, Tb) systems present layered-perovskite structure associated to layered ordering of Ln, Ba and Ca in combination with layered ordering of different oxygen-environments of the Fe atoms. The compounds with formula corresponding to x = 0, 0.25 and 0.4 do not contain anion vacancies but a stoichiometric oxygen sublattice, resulting the homologous series AFeO (A = Ln, Ba, Ca) with m, n = 1, 0; 1, 1; and 0, 1 respectively. The nature and ratio of the cations highly influence their ordering and the Fe-coordination polyhedra. In this sense, substitution of Ln by Y in the AFeO oxides might modify the A-layered ordering and/or the oxygen sublattice. YBaCaFeO, instead of stoichiometric YBaCaFeO, is prepared as single phase by ceramic method. Its characterization by means of transmission electron microscopy techniques indicates that, like in the LnBaCaFeO oxides, the Y, Ba and Ca are ordered within five different (00)-layers in combination with the ordering of the oxygen-polyhedra around the Fe-atoms in square-based pyramids, octahedra and tetrahedra along the c-axis. However, a different superstructure with unit cell, ascribed to the modulation of the [FeO] tetrahedra within the (00)-layers, is concluded for YBaCaFeO.

中文翻译：

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重新审视Y0.9Ba1.7Ca2.4Fe5O13层状钙钛矿的晶体结构：阳离子排序与阴离子亚晶格调制的新相互作用

LnBaCaFeO (Ln = Gd, Tb) 体系的氧化物呈现出层状钙钛矿结构，该结构与 Ln、Ba 和 Ca 的层状排列以及 Fe 原子不同氧环境的层状排列相关。对应于x = 0、0.25和0.4的式的化合物不含阴离子空位，而是含有化学计量的氧亚晶格，产生同系系列AFeO（A = Ln、Ba、Ca），其中m、n = 1、0； 1, 1;和 0、1 分别。阳离子的性质和比例极大地影响它们的排序和铁配位多面体。从这个意义上说，AFeO氧化物中Ln被Y取代可能会改变A层排序和/或氧亚晶格。采用陶瓷法制备单相 YBaCaFeO，代替化学计量的 YBaCaFeO。通过透射电子显微镜技术对其进行表征表明，与 LnBaCaFeO 氧化物一样，Y、Ba 和 Ca 在五个不同的 (00) 层内排序，并结合 Fe 原子周围氧多面体的排序。沿 c 轴的方形金字塔、八面体和四面体。然而，YBaCaFeO 的上层结构与晶胞不同，归因于 (00) 层内 [FeO] 四面体的调制。