Flux syntheses and single-crystal structures of CsNa$0$it M$$(AsO$$)$$ (it M = Zr, Hf)

William T. A. Harrison* (Corresponding Author)

*Corresponding author for this work

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Abstract

The isostructural compounds caesium decasodium tetrazirconium nonaarsenate, CsNa10Zr4(AsO4)9, and caesium decasodium tetrahafnium nonaarsenate, CsNa10Hf4(AsO4)9, arose as unexpected single-crystal products from the reactions of Na2CO3, MO2 (M = Zr, Hf) and As2O5 in a eutectic flux of NaCl and CsCl. They consist of MO6 octahedra and AsO4 tetrahedra sharing vertices to generate three-dimensional polyhedral networks encapsulating the caesium and sodium ions. The MO6 groups share all their vertices with adjacent As atoms but the As atoms have one or two ‘terminal’ O atoms not bonded to Zr or Hf. The Cs+ ion adopts a squashed octahedral geometry and the coordination polyhedra of the partially occupied sodium ions are variously trigonal bipyramidal, tetrahedral, square pyramidal and trigonal pyramidal. Site
symmetries: Cs 3; M 3; As 1 and 2; O 1; Na 1, 2 and 3. The M = Zr crystal
was refined as an obverse/reverse rhombohedral twin.
Original languageEnglish
Article numberE78
Number of pages14
JournalActa Crystallographica Section E
Volume78
Issue number7
Early online date1 Jul 2022
DOIs
Publication statusPublished - 1 Jul 2022

Bibliographical note

Acknowledgements
We thank the EPSRC National Crystallography Service (University of Southampton) for the X-ray data collection for (II).

Keywords

  • crystal structure
  • zirconium
  • hafnium
  • arsenate
  • ionic conduction

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