Hostname: page-component-586b7cd67f-gb8f7 Total loading time: 0 Render date: 2024-11-23T00:11:30.113Z Has data issue: false hasContentIssue false
  • English
  • Français

Structural characterization of anhydrous and bishydrated calcium hexafluorosilicate by powder diffraction methods

Published online by Cambridge University Press:  05 March 2012

Simone Frisoni ,
Stefano Brenna  and
Norberto Masciocchi
Simone Frisoni
Affiliation:
Dipartimento di Scienze Chimiche e Ambientali, Università dell’Insubria, via Valleggio 11, 22100 Como, Italy
Stefano Brenna
Affiliation:
Dipartimento di Scienze Chimiche e Ambientali, Università dell’Insubria, via Valleggio 11, 22100 Como, Italy
Norberto Masciocchi*
Affiliation:
Dipartimento di Scienze Chimiche e Ambientali, Università dell’Insubria, via Valleggio 11, 22100 Como, Italy
*
a)Author to whom correspondence should be addressed. Electronic mail: [email protected]
Get access Rights & Permissions [Opens in a new window]

Abstract

The synthesis and X-ray powder diffraction data for the long-known CaSiF6 and CaSiF6·2H2O species are reported. Their crystal structures have been determined from laboratory powder diffraction data by simulated annealing and full-profile Rietveld refinement methods. CaSiF6·2H2O was found to crystallize in the monoclinic P21/n space group with unit-cell parameters: a = 10.48107(9), b = 9.18272(7), c = 5.72973(5) Å, β = 98.9560(6)°, V = 544.733(8) Å3, and Z = 4. The crystal structure of CaSiF6·2H2O, eventually found to be isomorphous with SrSiF6·2H2O (but not with the Mg analogue—a hexahydrate phase), contains centrosymmetric [Ca(μ-H2O)2Ca]4+ dimers, interconnected by hexafluorosilicate anions, in a dense 3D framework. The crystal structure is completed by a further water molecule, terminally bound to the Ca2+ ion, which, consequently, attains a F5O3 octacoordination. Thermodiffractometric measurements allowed the determination of the linear and volumetric thermal expansion coefficients of CaSiF6·2H2O, which showed a minor contraction, along a, on heating. CaSiF6 is trigonal, space group R-3, a = 5.3497(3), c = 13.5831(11) Å, V = 336.66(5) Å3, and Z = 3, and isomorphous with several other species of MIIAIVF6 or MIAVF6 formulation, among which several silicates, germanates, and stannates.

Keywords

powder diffractioncalcium fluorosilicatestructure solutionRietveld refinementthermodiffractometry
Type
Technical Articles
Information
Powder Diffraction , Volume 26 , Issue 4 , December 2011 , pp. 308 - 312
Copyright
Copyright © Cambridge University Press 2011

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Altomare, A., Burla, M. C., Giacovazzo, C., Guagliardi, A., Moliterni, A. G. G., Polidori, G., Rizzi, R., (2001). “Quanto. A Rietveld Program for quantitative phase analysis of polycrystalline mixtures,” J. Appl. Crystallogr. 34, 392–397.10.1107/S0021889801002904CrossRefGoogle Scholar
Bruker AXS (2005). TOPAS-R Version 3, General profile and structure analysis software for powder diffraction data, Bruker AXS, Karlsruhe, Germany.Google Scholar
Coelho, A. A. (2000). “Whole-profile structure solution from powder diffraction data using simulated annealing,” J. Appl. Crystallogr. 22, 899–908.10.1107/S002188980000248XCrossRefGoogle Scholar
Structure Determination from Powder Diffraction Data, edited by David, W. I. F., Shankland, K., McCusker, L. B., and Baerlocher, C. (2005) (Oxford University Press, New York).Google Scholar
Golovastikov, N. I. and Belov, N. V. (1982). “The crystal structure of strontium fluosilicate dihydrate SrSiF6(H2O)2,” Kristallografiya 27, 649–650.Google Scholar
Hantson, P., Mahieu, P., Gersdorff, M., Sindic, C., and Lauwerys, R., (1995), “Fatal encephalopathy after otoneurosurgery procedure with an aluminum-containing biomaterial,” J. Toxicol. Clin. Toxicol 33, 645–648.10.3109/15563659509010622CrossRefGoogle ScholarPubMed
ICDD (2005). PDF-2 Release 2005 (Database), edited by McClune, W. F., International Centre for Diffraction Data, Newtown Square, PA.Google Scholar
Kawasaki, A., Ishikawa, K., Suge, T., Yoshiyama, M., Asaoka, K., and Ebisu, S. (1996). “Effects of hexafluorosilicate on the precipitate composition and dentine tubule occlusion by calcium phosphate,” J. Dent. (Oxford, U. K.) 24, 429–434.Google Scholar
Kirkpatrick, S., Gelatt, C. D., and Vecchi, M. P. (1983). “Optimization by simulated annealing,” Science 220, 671–680.10.1126/science.220.4598.671CrossRefGoogle ScholarPubMed
Kondrashev, Y. D. and Bogdanov, V. S. (1987). “Isostructural MII AIV F6B 2H2O compounds,” Russ. J. Inorg. Chem. 32, 337–338.Google Scholar
Masciocchi, N., Galli, S., and Sironi, A. (2005), “X-ray powder diffraction characterization of polymeric metal diazolates,” Comments Inorg. Chem. 26, 1–37.10.1080/02603590590920361CrossRefGoogle Scholar
National Bureau of Standards, NBS Monography N. 25 (1982), v. 19/31, Gaithersburg, MD.Google Scholar
Patil, K. C. and Secco, E. A. (1975). “Metal halide amines. III. Thermal analysis and calorimetry of fluorosilicate amines and hydrates of bivalent metals. Infrared spectra of the amines,” Can. J. Chem. 53, 2426–2429.10.1139/v75-343CrossRefGoogle Scholar
Shannon, D. and Prewitt, C. T. (1969). “Effective ionic radii in oxides and fluorides,” Acta Crystallogr., Sect. B: Struct. Crystallogr. Cryst. Chem. 25, 925–945.10.1107/S0567740869003220CrossRefGoogle Scholar
Zachara, J. and Wiśniewski, W. (1995), “Electronegativity force of cations and thermal decomposition of complex fluorides. I. Thermal decomposition of fluorisilicates,” J. Therm. Anal. 44, 363–373.10.1007/BF02636127CrossRefGoogle Scholar