inorganic compounds
Open access
The structure of the title compound trisodium aluminium bis(arsenate), Na3Al(AsO4)2, is built up from AlO4 and AsO4 corner-sharing tetrahedra, forming an undulating two-dimensional framework parallel to (100). The layers are constituted of large Al6As6O36 rings made up from six AlO4 and AsO4 tetrahedra in which two sodium cations are situated, the third sodium cation being located in the interlayer space. The structural relationships between the title compound and Na3Fe(PO4)2, NaAlCo(PO4)2 and Al5Co3(PO4)8 are discussed.
inorganic compounds
Open access
The title compound, heptasodium trialuminium tetrakis(diarsenate), has been isolated as single crystals from a solid-state reaction. Its structure, which is isotypic with that of the Na7Fe3(X2O7)4 (X = As, P) family of compounds, consists of AlO6 octahedra sharing their vertices with As2O7 groups, forming a three-dimensional [Al3(As2O7)4]∞ framework incorporating channels occupied by the sodium ions. One of the aluminium ions lies on a crystallographic twofold axis. The sodium ions are situated over ten positions (one with site symmetry 2), all but one of which are partially occupied.