Abdessalem Badri

RbCuFe(PO4)2.

A new iron phosphate, rubidium copper(II) iron(III) bis(phosphate), RbCuFe(PO4)2, has been synthesized as single crystals by the flux method. This compound is isostructural with KCuFe(PO4)2 [Badri et al. (2011 ▶), J. Solid State Chem. 184, 937–944]. Its structure is built up from Cu2O8 units of edge-sharing CuO5 polyhedra, interconnected by FeO6 octahedra through common corners to form undulating chains that extend infinitely along the [011] and [01-1] directions. The linkage of such chains is ensured by the PO4 tetraedra and the resulting three-dimensional framework forms quasi-elliptic tunnels parallel to the [101] direction in which the Rb+ cations are located.

CRYSTAL STRUCTURE AND THERMAL STABILITY OF NEW IRON PHOSPHATES KMFe(PO4)2 (M = Ni, Mg, and Co)

Three isostructural iron monophosphates KNiFe(PO4)2 (KNi), KMgFe(PO4)2 (KMg-LT, where LT means “low-temperature stable phase”), and KCoFe(PO4)2 (KCo-LT) are synthesized and structurally characterized from X-ray diffraction data. They crystallize in the monoclinic system with the space group P21/c. Their structures have in common a three-dimensional framework, built up by infinite zigzag chains of edge-sharing MO6 (M = Ni, Mg or Co) octahedra, linked by FeO5 and PO4 polyhedra via vertices and edges to form a rigid skeleton. The K+ ions are located in formed tunnels. DTA showed that KNi has a congruent melting at 941°C, whereas KMg-LT and KCo-LT undergo irreversible phase transitions from P21/c to different high-temperature structures with the C2/c symmetry. IR absorption bands are assigned to different vibrations of the PO4 tetrahedron.

RbZnFe(PO4)2: synthesis and crystal structure.

Rubidium zinc iron(III) phosphate is isostructural to KCoAl(PO4)2. Its structure consists of a three-dimensional framework built up from corner-sharing PO4 and (Zn,Fe)O4 tetrahedra. This mode of linkage forms tunnels parallel to the [100], [010] and [001] directions in which the Rb+ ions are located.

Synthesis and crystal structure of a new alluaudite-like iron phosphate Na2CaMnFe(PO4)3

Disodium calcium manganese iron tris(phosphate), Na2CaMnFe(PO4)3, crystallizes in the monoclinic space group C2/c. The structure belongs to the alluaudite structural type and thus, it obeys the X(2)X(1)M(1)M(2)2(PO4)3 general formula. Both the X(2) and X(1) sites are fully occupied by sodium, while M(1) is occupied by calcium and M(2) exhibits a statistical distribution of iron and manganese.

Synthesis and crystal structure of a new magnesium phosphate Na3RbMg7(PO4)6

Trisodium rubidium heptamagnesium hexakis(orthophosphate) exhibits a new structure type, with MgOx (x = 5 and 6) polyhedra linked directly to each other through common corners or edges and reinforced by corner-sharing with PO4 tetrahedra. The resulting anionic three-dimensional framework leads to the formation of channels in which the Na+ cations are located, while the Rb+ cations are located in large interstitial cavities.

Synthesis and crystal structure of NaMgFe(MoO4)3.

The iron molybdate NaMgFe(MoO4)3 is isostructural with α-NaFe2(MoO4)3 and its structure is built up from [Mg,Fe]2O10 units of edge-sharing [Mg,Fe]O6 octahedra which are linked to each other through the common corners of [MoO4] tetrahedra. The resulting anionic three-dimensional framework leads to the formation of channels along the [101] direction, where the Na+ cations are located.