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Crystals of dipotassium iron(III) tin(IV) tris(orthophosphate) were grown from a self-flux in the system K2O-P2O5-Fe2O3-SnO2. The title compound is isotypic with the mineral langbeinite, K2Mg2(SO4)3. Its three-dimensional [M2(PO4)3]∞ framework is composed of [MO6] (M = Sn, Fe) octahedra and [PO4] tetrahedra interlinked via vertices. In comparison with the previous refinement from X-ray powder data [Aatiq, Haggouch, Bakri, Lakhdar & Saadoune. (2006). Powder Diffr. 21, 214-219], the present reinvestigation from single-crystal data allows a more precise determination of the distribution of the Fe and Sn atoms over two crystallographic positions and a revision of the P-O and M-O [M = K, (Fe, Sn)] bond lengths. For the two K+ cations, two different polyhedra with coordination numbers of 9 and 12 are observed. The (Fe, Sn) and K atoms are located on three-fold axes. [ABSTRACT FROM AUTHOR]

Tetra­potassium cerium(IV) zirconium tetra­kis­(mono­phos­phate) crystallizes in the tetra­gonal system (space group I41/ amd). A complex disorder in K4CeZr(PO4)4 involves the mixing of Ce and Zr atoms on a single site with m2 symmetry and the splitting of P- and O-atom positions, equivalent to a rotation of the phosphate groups, to yield eight- and sixfold coordination environments around Ce and Zr, respectively. The K atoms are located in tunnels running parallel to the a and b axes. [ABSTRACT FROM AUTHOR]

Tetra­potassium cerium(IV) zirconium tetra­kis­(mono­phos­phate) crystallizes in the tetra­gonal system (space group I41/ amd). A complex disorder in K4CeZr(PO4)4 involves the mixing of Ce and Zr atoms on a single site with m2 symmetry and the splitting of P- and O-atom positions, equivalent to a rotation of the phosphate groups, to yield eight- and sixfold coordination environments around Ce and Zr, respectively. The K atoms are located in tunnels running parallel to the a and b axes. [ABSTRACT FROM AUTHOR]

Aliovalent KTP isomorphic compounds potassium chromium niobium oxide phosphate, KCr0.5Nb0.5OPO4, and potassium iron niobium oxide phosphate, KFe0.5Nb0.5OPO4, exhibit structures that differ from that of the non-centrosymmetric KTiOPO4. There are two crystallographically independent octa­hedral sites, M1 and M2, statistically occupied by Nb and Cr (or Fe) atoms. The M1O6 and M2O6 octa­hedra are connected alternately to form a chain with a cis– trans arrangement. The Nb atoms prefer the M2 sites arranged in a cis-like configuration. Each PO4 tetra­hedon has the P atom on a twofold axis. Site-splitting at the K-atom position is observed in both compounds. In the isomorphous structures, one Nb atom lies on an inversion centre and the other on a twofold axis. Similarly with the pairs of Fe/Cr sites, one is on an inversion centre and the other on a twofold axis. [ABSTRACT FROM AUTHOR]

The title compound, tris­odium titanium nitride tris­(phos­phate), is built up from TiIIIO6 octa­hedra linked together via [N(PO3)3] groups, the latter arising from three PO3N tetra­hedra sharing an N vertex. Three sodium cations complete the structure, which is also found for Na3AlN(PO3)3. All the metal cations and the N atom occupy special positions with site symmetry 3. [ABSTRACT FROM AUTHOR]