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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]

Dipotassium bismuth phosphate tungstate has been synthesized using the flux technique. It crystallizes in the space group Ibca and is isotypic with Na2Y(PO4)(MoO4). It exhibits a layered structure, which is built up from [Bi(PO4)(WO4)]∞2- layers. Each layer is composed of [BiO8]∞ zigzag chains, which are connected via PO4 and WO4 tetrahedra. The parallel anionic [Bi(PO4)(WO4)]∞2- layers are stacked along [100] and are held together by K+ counter-cations which occupy sites in the interlayer space. Bi, W and P atoms are all located on twofold axes. [ABSTRACT FROM AUTHOR]

Nonacalcium chromium(III) heptakis(orthophosphate) has been obtained from a melt in the system Cs2O–CaO–Cr2O3 using a polyphosphate flux. The three-dimensional framework is related to the whitlockite structure [β-Ca3(PO4)3] and is built up from CaO8 and CaO9 polyhedra sharing vertices, edges and faces, further connected by PO4 tetrahedra and CrO6 octahedra. The Cr, one P and one O atom are located on threefold rotation axes. Ca9Cr(PO4)7 is isotypic with Ca9Fe(PO4)7. The crystal studied was an inversion twin. [ABSTRACT FROM AUTHOR]