Raman spectroscopic and SEM analysis of sodium‐zippeite

Abstract

Raman at 298 and 77 K and infrared spectra of two samples of sodium-zippeite were studied and interpreted. U-O bond lengths in uranyl were calculated and compared with those inferred from the X-ray single crystal structure data of a synthetic sodium-zippeite analogue. Hydrogen-bonding network in the studied samples is discussed. O-H· · ·O bond lengths were calculated and compared with those predicted from the X-ray single crystal structure analysis.with their synthetic analogues were published in 1976 by Frondel et al. 5 Chemical composition, refractive indices and X-ray powder patterns were included in this paper. However, some confusion in these results were observed. O'Brien and Williams 12 and Haacke and Williams 13 presented G o f values for synthetic K-, (NH 4 )-, Na-, Mg-, Ni-, Co-and Znzippeites and assumed extensive solid solution formation between the divalent cation-containg zippeites, between Kand (NH 4 )-zippeites, but not between K-and Na-zippeites. Extensive crystallochemical and structural study of synthetic zippeites was recently published by Burns et al. 14 followed by a dissertation describing in detail some natural zippeites. 2 Both authors found that layered zippeites are topologically identical. The sheet contains zig-zag chains of edge-sharing uranyl pentagonal dipyramids and the chains are connected by the sharing of vertices between the uranyl pentagonal dipyramids and sulfate tetrahedra. Each sulfate tetrahedron is linked to four different uranyl dipyramids. 15 The sheet is made up of chains of uranyl pentagonal dipyramids that are two-polyhedra-wide. The chains are crosslinked through SO 4 2 tetrahedra, resulting in uranyl sulfate sheets. The composition of the sheet is dependant upon the distribution of O 2 / OH in each zippeite phase. 2 The uranyl sulfate sheets are in some cases (e.g. (NH 4 )-zippeites) anhydrous, [ UO 2 2 SO 2 O 2 ], or oxy anions may be partly substituted by hydroxyls e. g. in zippeite (the name zippeite proposed by Frondel et al. 5 for K-zippeite from Jáchymov, studied by Nováček in 1935, [ UO 2 4 SO 4 2 O 3 OH ], or in sodium-zippeite, [ UO 2 4 SO 4 4 O 5 OH 3 )]. 14,15 Burns et al. 14 concluded that the distribution of interlayer constituents, i.e. mono-and divalent cations and water molecules can

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“…The Gauss-Lorentz ratio was maintained at values greater than 0.7 and fitting was undertaken until reproducible results were obtained with squared correlations of r 2 greater than 0.995. Further details on the manipulation of the data has been published [10][11][12][13][14][15][16][28][29][30] .…”

Raman spectroscopic study of the tellurite minerals: Carlfriesite and spiroffite

“…• Author to whom correspondence should be addressed (r.frost@qut.edu.au) 2 A 2 (XO 3 ) 3 .xH 2 Raman spectroscopy has proven very useful for the study of minerals [25][26][27][28][29][30][31][32][33][34][35].…”

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