Structural Analysis of Zirconium Hydroxide Nitrate Monohydrates by X-Ray Powder Diffraction
1997; Elsevier BV; Volume: 128; Issue: 2 Linguagem: Inglês
10.1006/jssc.1996.7226
ISSN1095-726X
AutoresPatricia Bénard-Rocherullé, Jordi Rius, D. Louër,
Tópico(s)Radioactive element chemistry and processing
ResumoThe crystal structures of α-Zr(OH)2(NO3)2· 1.65H2O and β-Zr(OH)2(NO3)2· H2O were determinedab initiofrom laboratory X-ray powder diffraction data. The two zirconium hydroxide nitrates crystallize with triclinic unit cells (P1) with the parameters:a=10.051(3) Å,b=10.357(3) Å,c=8.131(2) Å, α=108.30(2)°, β=112.02(2)°, γ=79.75(3)° for the α phase, anda=9.180(3) Å,b=10.465(4) Å,c=8.076(2) Å, α=109.58(3)°, β=98.96(3)°, γ=80.43(3)° for the β phase. An interpretation of the Patterson functions led to the location of two independent Zr atoms for the α and β forms. The light atom coordinates were determined from successive three-dimensional Fourier maps. The structure of α-Zr(OH)2(NO3)2·1.65H2O is built from edge sharing ZrO8trigonal dodecahedra, through double hydroxyl bridges, to form infinite neutral zigzag chains of chemical composition [Zr(OH)4/2(NO3)2]n, running along [011]. The 8-fold coordination of each Zr atom is completed by four oxygens from bidentate nitrate groups. They are involved in a complex hydrogen bonding network occurring between the chains via “free” water molecules. The loss of the weakly bonded water molecule leads to the β form without collapse of the 1D framework of the precursor. In the β variety, the 8-fold coordination is preserved for the two Zr atoms. However, the exact shapes of the polyhedra have not been precisely defined.
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