DSC, structural single crystal and X-ray powder diffraction study of the ammonium sulfate selenate tellurate mixed solid solution

Crystal structure of (NH4)(2)(SO4)(0.73)(SeO4)(0.27)Te(OH)(6) (NSSeTe) crystallizes in the monoclinic P2(1)/c space group. It was analyzed at room temperature using X-ray diffractorneter data. The unit cell parameters are a=13.7340(2)angstrom, b=6.6583(1)angstrom, c=11.4582(2)angstrom, beta=106.8270(6)degrees, Z=2, V=1002.93(3) angstrom(3), R=0.014, R-w=0.017 and D-x=2.426g cm(-3). The main feature of this atomic arrangements is the coexistence of three different anions (SO42-, TeO66- and SeO42- groups) in the unit cell, connected by hydrogen bonds which make the building of the crystal. The distribution of atoms can be described as isolated TeO6 octahedra and SO4 and/or SeO4 tetrahedra occupying the same positions. The NH4+ cations, are located between these polyhedra. The molecular species present in the lattice are S/SeO42- tetrahedra and TeO66- octahedra disposed in a number of sheets. The thermal analysis of the title compound show three distinct endothermal peaks at 398, 430 and 450 K. X-ray powder diffraction data at different temperatures confirm that. the first anomaly at 398 K can be attributed to a structural phase transition. (C) 2007 Elsevier B.V All rights reserved.