Na₃Al(AsO₄)₂

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.