X-RAY-POWDER STRUCTURE OF MONOAMMONIUM-EXCHANGED PHASE OF GAMMA-ZIRCONIUM PHOSPHATE, ZR(PO4)(NH4HPO4)

The monoammonium salt of gamma-zirconium phosphate has been prepared, and its structure was solved by using X-ray powder diffraction data. T he positions of the Zr and one of the P atoms were located from a Patt erson map computed by using 29 unambiguously indexed reflections. Full pattern analysis using these two atoms and subsequent difference Four ier maps allowed the location of all the remaining atoms in the struct ure, including, the position of the nitrogen atom of the ammonium ion. Zr(PO4)(NH4HPO4) crystallizes in the monoclinic space group P2(1)/m w ith a 5.3284(4) Angstrom, b = 6.6217(2) Angstrom, c = 11.326(1) Angstr om, beta = 96.63(1)degrees, and Z = 2. The final agreement factors are R(wp) = 0.105, R(p) = 0.081, and R(F) = 0.043. The structure consists of metal phosphate layers forming the ab plane. The metal atoms and o ne of the phosphate groups are located nearly in the plane of this lay er. All the oxygen atoms of this phosphate group are involved in metal coordination. The other phosphate group links two Zr atoms in the a-d irection through two of its oxygen atoms. The remaining two oxygens, w hich constitute hydroxyl groups in the parent gamma-ZrP, are projected into the interlayer space and are hydrogen bonded to the ammonium ion s. Additionally, there are direct interactions between adjacent layers in the form of hydrogen bonds among these oxygens. Each ammonium ion is shared by four oxygens from four different phosphate hydroxyl group s.