Matsui Y, Akimitsu J
National Institute for Research in Inorganic Materials, Ibaraki, Japan.
Microsc Res Tech. 1995 Feb 1;30(2):155-66. doi: 10.1002/jemt.1070300206.
Arrangements of CO3 groups in various types of oxycarbonate superconductors are examined by high-resolution transmission electron microscopy (HRTEM). Every other B-site of basic perovskite structure is replaced with CO3 groups in the first carbonate superconductor, (Ba0.56Sr0.44)2Cu1.1(CO3)0.9Oy. The 123-related oxycarbonate superconductor obtained in a Y-Ca-Sr-Cu-O system, (Y0.475Ca0.475Sr0.05)Sr2Cu2.4(CO3)0.6Oy, has a superstructure with 2a periodicity due to ordered replacements of Cu-site with CO3 groups. The non-superconducting counterpart with 123-related structure, (Y0.84Sr0.16)2Sr2Cu2.6(CO3)0.4Oy, on the other hand, shows more disordered arrangements of CO3 groups with nearly 3a periodicity. Similar superstructures, due to ordered replacements of Cu sites with CO3 groups, are also observed in the 223-related oxycarbonate superconductors, (Ln,Ce)2Sr2Cu2.5(CO3)0.5Oy (Ln = Ho, Dy). Homologous series of compounds, (CaSr)n+1Cun(CO3)Oy (n = 1-5), consist of alternate stacking of Sr2Cu(CO3)Oy and SrCuO2 (infinite-layer) types of blocks. They become superconductive by additionally doping the BO3 group. Another homologous series of Bi-based oxycarbonate superconductors, (Bi,Pb)2Sr2n+2Cun+1 (CO3)nOy (n = 1-3), contain alternate CuO2 and CO3 layers in between the two (BiO)2 layers. Both mercury (Hg)- and thallium (TI)-based oxycarbonate superconductors, MBa2Sr2Cu2(CO3)Oy (M = Hg or Tl) show quite unique modulation structures, where both HgO (or TlO) and CO3 layers repeat in the same plane, along [110] in the Hg compound and [100] in the Tl compound, to form long-period superstructures with wavy distortion of atom planes.
通过高分辨率透射电子显微镜（HRTEM）研究了各种类型的氧碳酸盐超导体中碳酸根（CO₃）基团的排列方式。在首个碳酸盐超导体（Ba₀.₅₆Sr₀.₄₄）₂Cu₁.₁(CO₃)₀.₉O_y中，基本钙钛矿结构的每隔一个B位被CO₃基团取代。在Y-Ca-Sr-Cu-O体系中获得的与123相关的氧碳酸盐超导体（Y₀.₄₇₅Ca₀.₄₇₅Sr₀.₀₅）Sr₂Cu₂.₄(CO₃)₀.₆O_y，由于CO₃基团对铜位点的有序取代，具有2a周期性的超结构。另一方面，具有123相关结构的非超导对应物（Y₀.₈₄Sr₀.₁₆）₂Sr₂Cu₂.₆(CO₃)₀.₄O_y，显示出CO₃基团更无序的排列，具有近3a周期性。在与223相关的氧碳酸盐超导体（Ln,Ce）₂Sr₂Cu₂.₅(CO₃)₀.₅O_y（Ln = Ho, Dy）中，也观察到由于CO₃基团对铜位点的有序取代而形成的类似超结构。同系化合物（CaSr）ₙ₊₁Cuₙ(CO₃)O_y（n = 1 - 5）由Sr₂Cu(CO₃)O_y和SrCuO₂（无限层）类型的块交替堆叠组成。通过额外掺杂BO₃基团，它们会变成超导的。另一系列基于铋的氧碳酸盐超导体（Bi,Pb）₂Sr₂ₙ₊₂Cuₙ₊₁(CO₃)ₙO_y（n = 1 - 3），在两个（BiO）₂层之间包含交替的CuO₂和CO₃层。基于汞（Hg）和铊（Tl）的氧碳酸盐超导体MBa₂Sr₂Cu₂(CO₃)O_y（M = Hg或Tl）都显示出非常独特的调制结构，其中HgO（或TlO）和CO₃层在同一平面内重复，在Hg化合物中沿[110]方向，在Tl化合物中沿[100]方向，形成原子平面呈波浪状畸变的长周期超结构。
