Structural, magnetic, and ion-exchange properties of a new layered alkaline/alkaline earth iron phosphate: NaBaFe4(HPO4)3(PO4)3.H2O.

A new mixed alkali/alkaline earth iron phosphate, NaBaFe4(HPO4)3.H2O, has been synthesized hydrothermally and structurally characterized by single-crystal X-ray diffraction, magnetic susceptibility, infrared spectroscopy, and thermogravimetric analysis. The title compound crystallizes in the monoclinic space group P2(1)/c (No. 14) with a = 9.287(2) A, b = 22.665(4) A, c = 8.966(3) A, beta = 91.82(2), and Z = 4. The compound has a 2-D framework structure constructed from layers, stacked along the [010] unit cell direction with Na+ and Ba2+ ions, and water molecules residing within the interlayer space. The anionic layers are composed from the assemblage of vertex shared FeO6 octahedra interconnected by PO4(3)- and HPO4(2)- tetrahedra. The layers are built from four unique FeO6 units linking through vertex shared oxygen atoms to form infinite zigzag chains that run parallel to the a axis. These chains form single layers that run infinitely in the c direction through the vertex sharing of PO4 groups.