Polytypism in Sulfate-Intercalated Layered Double Hydroxides of Zn and M(III) (M = Al, Cr): Observation of Cation Ordering in the Metal Hydroxide Layers

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• 作者：S. Radha ; P. Vishnu Kamath
• 刊名：Inorganic Chemistry
• 出版年：2013
• 出版时间：May 6, 2013
• 年：2013
• 卷：52
• 期：9
• 页码：4834-4841
• 全文大小：369K
• 年卷期：v.52,no.9(May 6, 2013)
• ISSN：1520-510X

文摘

The as-precipitated sulfate-intercalated layered double hydroxide of Zn and Al crystallizes in the structure of the 3R₁ polytype. On hydrothermal treatment, this 3R₁ polytype transforms into the somewhat rare 3H and 3R₂ polytypes at different temperatures. Observation of the 3R₂ polytype distinct from the 3R₁ polytype is evidence for the lack of cation ordering in the [Zn鈥揂l鈥揝O₄] system. The layered double hydroxide of Zn and Cr (polytype, 1H) on hydrothermal treatment in mother liquor yields a cation-ordered phase also having the structure of the 1H polytype. Direct evidence of cation ordering is found by the appearance of weak supercell reflections corresponding to a = 鈭? 脳 a_o (a_o is the a parameter of the cation-disordered phase). The same precursor under other conditions yields the cation-disordered 3R₁ polytype. In this work, the structures of both the cation-ordered and the cation-disordered phases with similar states of hydration are refined and compared.