Research Article: Na7Mg13Nd(PO4)12

Date Published: June 01, 2012

Publisher: International Union of Crystallography

Author(s): Hasna Jerbi, Mourad Hidouri, Ben Amara Mongi.


Investigations of the quasi-ternary system Na3PO4–Mg3(PO4)2–NdPO4 allowed us to obtain the new phosphate hepta­sodium trideca­magnesium neodymium dodeca­kis­phosphate, Na7Mg13Nd(PO4)12, by applying a flux method. The crystal structure is isotypic with that of the previously reported Na7Mg13Ln(PO4)12 (Ln = Eu, La) compounds. It consists of a complex three-dimensional framework built up from an NdO8 polyhedron (m symmetry), an MO6 octa­hedron statistically occupied by M = Mg and Na, and eight MgOx (x = 5, 6) polyhedra (four with site symmetry m), linked either directely by sharing corners, edges and faces, or by one of the eight unique PO4 tetra­hedra through common corners. Two of the PO4 tetra­hedra are statisticaly disordered over a mirror plane. The whole structure can be described as resutling from an assembly of two types of structural units, viz [Mg4MP4O22]∞2 layers extending parallel to (100) and stacked along [100], and [Mg4NdP4O36]∞1 undulating chains running along the [010] direction. The six different Na+ cations (five with site symmetry m and one with 0.5 occupancy) are situated in six distinct cavities delimited by the framework. The structure was refined from data of a racemic twin.

Partial Text

For the synthesis and luminescent properties of new phosphates for optical devices, see: Ngee et al. (2009 ▶); Shinde et al. (2011 ▶). The title structure is isotypic with Na7Mg13Ln(PO4)12 (Ln = La, Eu) (Jerbi et al., 2010 ▶). For P—O distances in orthophosphates, see: Baur (1974 ▶). For Mg—O distances, see: Ben Amara et al. (1983 ▶); Jaulmes et al. (1997 ▶); Klevtsova et al. (1980 ▶), For Na—O distances, see: Donnay & Allmann (1970 ▶), and for Nd—O distances, see: Albrand et al. (1974 ▶).