Synthesis and Crystal Structure of Fluoride K2(Ta0.9I0.1)F7 with the Micro-Isomorphic Substitution in the Ta Cationic Position

• Published in: Crystallography reports 2022-12, Vol.67 (7), p.1122-1126
• Main Authors: Reutova, O. V., Belokoneva, E. L., Dimitrova, O. V., Volkov, A. S.
• Format: Article
• Language: English
• Subjects: Cations; Crystal structure; Crystallography and Scattering Methods; Hydrothermal crystal growth; Isomorphism; Physics; Physics and Astronomy; Structure of Inorganic Compounds; Synthesis
• ISSN: 1063-7745; 1562-689X
• DOI: 10.1134/S1063774522070264

Fluoride crystals K 2 (Ta 0.9 I 0.1 )F 7 (sp. gr. Р 2 1 / c ) complementary to the K 2 TaF 7 and K 2 NbF 7 fluoride family have been obtained by hydrothermal synthesis. Their structure contains isolated (TaF 7 ) 2‒ polyhedral blocks, the charge of which is compensated by K + cations located between them. A small amount of the I 5+ impurity has been found in the Та 5+ site, which is atypical of this pair of elements. An example of such isomorphism is the occurrence of I 5+ in the Ge 4+ site in the K 4 [Ge 0.85 I 0.12 0.03 ]Ge 5 O 20 germanate octahedron. The synthesis conditions have led to the separation of the initial components into two phases, fluoride K 2 (Ta 0.9 I 0.1 )F 7 and iodate KIO 3 , without formation of the expected iodate fluorides.