Investigation of reactivity and structure formation in a K-Te-U oxo-system under high-temperature/high-pressure conditions

The high-temperature/high-pressure treatment of the K-Te-U oxo-family at 1100 °C and 3.5 GPa results in the crystallization of a series of novel uranyl tellurium compounds, K₂[(UO₂)₃(Te^IVO₃)₄], K₂[(UO₂)TeO₁₄], α-K₂[(UO₂)Te^VIO₅] and β-K₂[(UO₂)Te^VIO₅]. In contrast to most of the reported uranyl compounds which are favorable in layered structures, we found that under extreme conditions, the potassium uranyl oxo-tellurium compounds preferably crystallized in three-dimensional (3D) framework structures with complex topologies. Anion topology analysis indicates that the 3D uranyl tellurite anionic framework observed in K₂[(UO₂)₃(Te^IVO₃)₄] is attributable to the additional linkages of TeO₃ polyhedra connecting with TeO₄ disphenoids from the neighboring U-Te layers. The structure of K₂[(UO₂)TeO₁₄] can be described based on [UTe₆O₂₆]^22- clusters, where six TeO₅ polyhedra enclose a hexagonal cavity in which a UO₈ polyhedron is located. The [UTe₆O₂₆]^22- clusters are further linked by TeO₅ square pyramids to form the 3D network. Similar to uranyl tellurates, both α-K₂[(UO₂)Te^VIO₅] and β-K₂[(UO₂)Te^VIO₅] contain TeO₆ octahedra which share a common face to form a dimeric Te₂O₁₀ unit. However, in α-K₂[(UO₂)Te^VIO₅], these Te₂O₁₀ units connect with UO₆ tetragonal bipyramids to form a 3D structural framework, while in β-K₂[(UO₂)Te^VIO₅], the same Te₂O₁₀ dimers are observed to link with UO₇ pentagonal bipyramids, forming 2D layers. Raman measurements were carried out and the vibration bands related to Te^IV-O, Te^VI-O and U^VI-O bonds are discussed.

Efficiently synthesized Co doped Cu3TeO6 accounted for its anomalous behaviour in electronic properties

Efficient synthesis of Cu_3−xCo_xTeO₆ (x = 0.0, 0.1, 0.3 or 0.5) yields cubic morphologies, which exhibit remarkable electronic and enhanced permittivity properties.

Effect of the cation size on the framework structures of magnesium tungstate, A4Mg(WO4)3 (A = Na, K), R2Mg2(WO4)3 (R = Rb, Cs)

A series of alkali metal magnesium tungstates, A₄Mg(WO₄)₃ (A = Na, K), R₂Mg₂(WO₄)₃ (R = Rb, Cs), were synthesized from a high temperature solution, and their structures were determined by single-crystal X-ray diffraction.