Kuma K, Usui A, Paplawsky W, Gedulin B, Arrhenius G
Department of Chemistry, Hokkaido University, Japan.
Mineral Mag. 1994 Sep;58(4):425-47. doi: 10.1180/minmag.1994.058.392.08.
The crystal structures of synthetic 7 angstrom and 10 angstrom manganates, synthetic birnessite and buserite, substituted by mono- and divalent cations were investigated by X-ray and electron diffractions. The monoclinic unit cell parameters of the subcell of lithium 7 angstrom manganate, which is one of the best ordered manganates, were obtained by computing the X-ray powder diffraction data: a = 5.152 angstroms, b = 2.845 angstroms, c = 7.196 angstroms, beta = 103.08 degrees. On the basis of the indices obtained by computing the X-ray diffraction data of Li 7 angstrom manganate, monovalent Na, K and Cs and divalent Be, Sr and Ba 7 angstrom manganates were interpreted as the same monoclinic structure with beta = 100-103 degrees as that of Li 7 angstrom manganate, from their X-ray diffraction data. In addition, divalent Mg, Ca and Ni 10 angstrom manganates were also interpreted as the same monoclinic crystal system with beta=90-94 degrees. The unit cell parameters, especially a, c and beta change possibly with the type of substituent cation probably because of the different ionic radius, hydration energy and molar ratio of substituent cation to manganese. However, these diffraction data, except for those of Sr and Ba 7 angstrom and Ca and Ni 10 angstrom manganates, reveal only some parts of the host manganese structure with the edge-shared [MnO6] octahedral layer. On the other hand, one of the superlattice reflections observed in the electron diffractions was found in the X-ray diffraction lines for heavier divalent cations Sr and Ba 7 angstrom and Ca and Ni 10 angtrom manganates. The reflection presumably results from the substituent cation position in the interlayer which is associated with the vacancies in the edge-shared [MnO6] layer and indicates that the essential vacancies are linearly arranged parallel to the b-axis. Furthermore, the characteristic superlattice reflection patterns for several cations, Li, Mg, Ca, Sr, Ba and Ni, manganates were interpreted that the substituent cations are regularly distributed in the interlayer according to the exchange percentage of substituent cation to Na+. In contrast, the streaking in the a-direction observed strongly in the electron diffractions for heavier monovalent cations, K and Cs, manganates probably results from the disordering of their cations in the a-direction in the interlayer.
通过X射线和电子衍射研究了由单价和二价阳离子取代的合成7埃和10埃锰酸盐、合成水钠锰矿和水羟锰矿的晶体结构。锂7埃锰酸盐是有序度最高的锰酸盐之一，通过计算X射线粉末衍射数据得到其亚晶胞的单斜晶胞参数：a = 5.152埃，b = 2.845埃，c = 7.196埃，β = 103.08°。根据计算锂7埃锰酸盐的X射线衍射数据所得指数，从其X射线衍射数据来看，单价的Na、K和Cs以及二价的Be、Sr和Ba 7埃锰酸盐被解释为与锂7埃锰酸盐具有相同的单斜结构，β = 100 - 103°。此外，二价的Mg、Ca和Ni 10埃锰酸盐也被解释为具有相同的单斜晶体系统，β = 90 - 94°。晶胞参数，尤其是a、c和β可能会随取代阳离子的类型而变化，这可能是由于取代阳离子的离子半径、水合能以及取代阳离子与锰的摩尔比不同所致。然而，除了Sr和Ba 7埃以及Ca和Ni 10埃锰酸盐的衍射数据外，这些数据仅揭示了具有边共享[MnO6]八面体层的主体锰结构的某些部分。另一方面，在电子衍射中观察到的超晶格反射之一在较重的二价阳离子Sr和Ba 7埃以及Ca和Ni 10埃锰酸盐的X射线衍射线中也被发现。该反射可能是由于取代阳离子在层间的位置与边共享[MnO6]层中的空位相关，这表明基本空位沿b轴方向呈线性排列。此外，对几种阳离子（Li（锂）、Mg（镁）、Ca（钙）、Sr（锶）、Ba（钡）和Ni（镍））的锰酸盐的特征超晶格反射模式进行了解释，即取代阳离子根据取代阳离子与Na +的交换百分比在层间规则分布。相比之下，在较重的单价阳离子K（钾）和Cs（铯）的锰酸盐的电子衍射中强烈观察到的a方向上的条纹可能是由于它们的阳离子在层间a方向上的无序排列所致。
