Synthesis and Characterization of Hollandite Type Compounds

荷兰酸类化合物的化学式一般为<A_x(M^(3+)M^(2+))_yM_(8-y)O_(16)> (0<x<2)。阳离子M （Mn、Ti、Fe、Al等）位于氧的八面体位置上，构成了八面体的双弦结构。四根弦使一维隧道结构形成四边形棱镜。大阳离子A （K,Na，Ba等）占据了氧的准立方位置。这类化合物有望用于一维离子导体、吸收剂和捕获放射性废物大离子（Cs等）的SYNROC。在这项工作中，合成了这种类型化合物的晶体，并对其进行了表征，以了解隧道。第一年首次在880℃的空气中采用固相反应合成了荷兰石（<Ba_xMn_8O_(16)>, 1.23<x<1.36）。虽然这种化合物存在于自然界，但迄今为止还没有人合成过。随着温度的升高，荷兰石的占用率由低变为高。这一现象已在隐叶兰中观察到。第二年合成了隐木烯（<K_xMn_8O_(16)>, 1.0<x<2.0）的固溶体，并通过差热分析得到了其组成与分解温度的关系。高入住率的隐黑蝇在热水中放置3周，其入住率下降了60%左右。自然界中天然隐黑烷的k离子位点占比约为50%。可能是天然隐黑素被天然水冲走了，然后k离子位置的占用率下降了一半。这些信息对于了解隧道结构非常有用。

Chemical formula of hollandite type compounds is generally <A_x(M^(3+)M^(2+))_yM_(8-y)O_(16)> (0<x<2). Cations M (Mn, Ti, Fe, Al etc.) locate on the octahedral sites of oxygen and construct double strings of octahedron. The four strings make one dimensional tunnel structure formed tetragonal prism. Large cations A (K,Na,Ba etc.) occupy on the pseudo-cube sites of oxygen. It is expected that this type compounds are used for one dimensional ion conductor, absorbent and SYNROC which trap radioactive waste large ions (Cs, etc.). In this work, crystals of this type compound were synthesized and were characterized for understanding of the tunnel. In the first year, hollandite ( <Ba_xMn_8O_(16)> , 1.23<x<1.36) was synthesized for the first time in the air up to 880 C by means of solid state reaction. Although the compound exists in nature, it had never been synthesized so far. The occupancy of hollandite was changed from low to high occupancy according as the temperature increases. This phenomena had been observed in cryptomelane. In the next year, solid solutions of cryptomelane ( <K_xMn_8O_(16)> , 1.0<x<2.0) were synthesized and the relationship between the compositions and the decomposition temperatures of them was derived by DTA. The occupancy of cryptomelane with high occupancy was decreased up to about 60% in the hot water for three weeks. The occupancy of K-ion sites of natural cryptomelane is about 50% in nature. Perhaps natural cryptomelane was washed out by natural water and then the occupancy of K-ion sites fell to half. These informations were very available for understanding the tunnel structure.