Synthesis and structure of the new ammonium indium phosphate (NH4)In(OH)PO4

A new ammonium indium phosphate (NH4)In(OH)PO4 was prepared by hydrothermal reaction in the In2O3-NH4H2PO4-NH3/OH system (T = 200degreesC, autogenous pressure, 7 days). The formula (NH4)In(OH)PO4 was determined on the basis of chemical and thermal analysis (TG/DSC), X-ray powder diffraction and IR-spectroscopy. (NH4)In(OH)PO4 crystallizes in the tetragonal system with space group P4(3)2(1)2 (No. 96), a - 9.4232(1) Angstrom, 11. 1 766(1) Angstrom, V = 992.45(2) Angstrom(3); Z= 8. The crystal structure was refined by the Rietveld method (R-w = 6.35%, R-p = 5.10%). The second-harmonic generation study confirmed that structure of (NH4)In(OH)PO4 does not have a center of symmetry. The cis-InO4(OH)(2) octahedra form helical chains, parallel to the c-axis. The In-O-In bonds are nearly equidistant. The chains are interconnected by phosphate tetrahedra and create tunnels containing the NH4+ ions along the c-axis. (NH4)In(OH)PO4 is isostructural with RbIn(OH)PO4. (C) 2002 Elsevier Science (USA).