Novel aluminophosphate Na6[Al3P5O20] with the original microporous crystal structure established in the study of a pseudomerohedric microtwin. Issue 2 (17th March 2021)

• Record Type: Journal Article
• Authors: Yakubovich, Olga V.; Kiriukhina, Galina V.; Volkov, Anatoliy S.; Dimitrova, Olga V.; Borovikova, Elena Yu.
• Is Part Of: Acta crystallographica. Volume 77:Issue 2(2021)
• Page Start: 232
• Page End: 240
• Publication Date: 2021-03-17
• Subjects: crystal structure -- X‐ray diffraction -- IR spectroscopy -- sodium aluminophosphate -- microporous zeolite -- pseudomerohedric twin -- hydrothermal/solvothermal synthesis -- crystal chemistry -- rod packing
• DOI: 10.1107/S2052520621001785
• Languages: English
• ISSNs: 2052-5206

Abstract

Abstract : Microporous sodium aluminophosphate, Na6 [Al3 P5 O20 ], with a new type of structure, is described as being built of octahedral rods arranged in two perpendicular directions. Abstract : The synthesis and characterization of a new aluminophosphate, Na6 [Al3 P5 O20 ], obtained as single crystals in the same experiment together with Cl‐sodalite, Na8 [Al6 Si6 O24 ]Cl2, is reported. Na6 [Al3 P5 O20 ], with a strongly pseudo‐orthorhombic lattice, is described by the monoclinic crystal structure established in the study of a pseudomerohedric microtwin. The design of Na6 [Al3 P5 O20 ] can be interpreted as an alternative to sodalite, with a monoclinic (pseudo‐orthorhombic) 2×4×1 super‐structure and unit‐cell parameters multiples of those of sodalite: a ≃ 2 a s, b ≃ 4 b s and c ≃ c s . The triperiodic framework is built by AlO6, AlO4 and PO4 polyhedra having vertex‐bridging contacts. While all the oxygen vertices of the Al‐centred octahedra and tetrahedra are shared with phosphate groups, some of the PO4 tetrahedra remain `pendant', e.g. containing vertices not shared with other polyhedra of the aluminophosphate construction. Na atoms occupy framework channels and cavities surrounded by eight‐, six‐ and four‐membered windows with maximal effective pore widths of 4.86 × 3.24 and 4.31 × 3.18 Å. The generalized framework density is equal to 19.8, which means that the compound may be classified as a microporous zeolite. The Na6 [Al3 P5 O20 ] crystal structure is discussed as being formed from octahedral rods arranged in two perpendicular directions, similar to the rods elongated in one direction in the NASICON‐type compounds, which have been intensively investigated as promising materials for batteries. Analogous properties can be expected for phases with a modified composition of the Na6 Al3 P5 O20 topology, where the Al atoms at the centres of octahedra are replaced by Fe, V or Cr.