X-ray powder structure and Rietveld refinement of the monosodium exchanged monohydrate of .alpha.-zirconium phosphate, Zr(NaPO4)(HPO4).cntdot.H2O
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The crystal structure of the partially hydrated monosodium-exchanged phase of a-zirconium phosphate, Zr(HPO4)2·H2O, has been determined by using data collected on a conventional computer-controlled X-ray powder diffractometer. The positions of all atoms in the layer were determined by using 40 unambiguously indexed reflections, obtained by pattern decomposition, in a conventional single-crystal type analysis. Whole-pattern (Rietveld) analysis was then conducted to Rwp= 0.156 and resulted in the location and refinement of the exchanged Na+ion and the water oxygen in the interlamellar space. Zr(NaPO4)(HPO4)·H2O is monoclinic, P21/c, with cell parameters a = 8.8264 (2) Å, b = 5.3494 (1) Å, c = 16.0275 (6) Å, β= 101.857 (4)°, and Z = 4. The structure is a modification of the parent a-zirconium phosphate with a shift of adjacent layers and twisting of the phosphate groups. This results in an altered cavity arrangement. Na+lies in a distorted octahedral environment, as does the water oxygen, 012. This arrangement of atoms in the interlamellar region is in an ordered manner similar to that in Zr(NH4PO4)2·H2O. Loss of the 1 mol of water results in a change in space group, and a mechanism for this transformation as well as that of the exchange process will be described. © 1989, American Chemical Society. All rights reserved.
author list (cited authors)
Rudolf, P. R., & Clearfield, A.