Rich Non-centrosymmetry in a Na–U–Te Oxo-System Achieved under Extreme Conditions

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• 作者：Bin Xiao ; Philip Kegler ; Dirk Bosbach ; Evgeny V. Alekseev
• 刊名：Inorganic Chemistry
• 出版年：2016
• 出版时间：May 2, 2016
• 年：2016
• 卷：55
• 期：9
• 页码：4626-4635
• 全文大小：621K
• 年卷期：0
• ISSN：1520-510X

文摘

Two new sodium uranyl tellurites and two new sodium uranyl tellurates have been synthesized from high-temperature/high-pressure conditions and structurally characterized. We demonstrated that crystalline phases, forming in a Na–U–Te system under extreme conditions, appear to favorably have non-centrosymmetric structures. Three out of four novel uranyl tellurium compounds, Na[(UO₂)Te^IV₂O₅(OH)], Na₂[(UO₂)(Te^VI₂O₈)], and Na₂[(UO₂)Te^VIO₅], crystallize in non-centrosymmetric space groups. The crystal structure of Na[(UO₂)Te^IV₂O₅(OH)] is based on two-dimensional [UO₂Te₂O₅(OH)]⁻ corrugated sheets, which are charge balanced by guest Na⁺ cations. The structure of Na₂[(UO₂)Te^VI₂O₈] is constructed from [(UO₂)₂Te₂O₈]²⁺ anionic layers composed of UO₇ pentagonal bipyramids and TeO₆ octahedra. Na₂[(UO₂)(Te^VIO₅)] is a new type of three-dimensional anionic open framework built from the interconnection of UO₇ pentagonal bipyramids and TeO₆ octahedra with different types of interlacing channels within the U–Te anionic framework. Na[(UO₂)Te^IV₆O₁₃(OH)], as the only centrosymmetric compound isolated in the Na–U–Te family, is crystallized in space group Pa3̅, and its structure is highly related to that of cliffordite (UO₂(Te₃O₇)), which is composed from UO₈ hexagonal bipyramids and TeO₅ square pyramids. The vibrational modes associated with U–O, Te^IV–O, and Te^VI–O bonds are discussed, and the Raman spectra of the four compounds are characterized for signature bands.