Hostname: page-component-586b7cd67f-rcrh6 Total loading time: 0 Render date: 2024-11-26T16:03:21.507Z Has data issue: false hasContentIssue false
  • English
  • Français

Crystal structures of room- and low-temperature phases in oxyfluoride (NH4)2KWO3F3

Published online by Cambridge University Press:  01 March 2012

M. S. Molokeev ,
A. D. Vasiliev  and
A. G. Kocharova
M. S. Molokeev
Affiliation:
L. V. Kirensky Institute of Physics, SB RAS, Krasnoyarsk 660036, Russia
A. D. Vasiliev
Affiliation:
L. V. Kirensky Institute of Physics, SB RAS, Krasnoyarsk 660036, Russia
A. G. Kocharova
Affiliation:
L. V. Kirensky Institute of Physics, SB RAS, Krasnoyarsk 660036, Russia
Get access Rights & Permissions [Opens in a new window]

Abstract

Crystal structures of (NH4)2KWO3F3 at 298 K and 113 K were solved from X-ray powder diffraction data and refined by the Rietveld technique. The compound is isostructural with elpasolite K2NaAlF6 at room temperature with space group Fm-3m, a=8.95850(5) Å, V=718.961(7) Å3, Z=4, Dx=3.363 g/cm3, and MW=364.02. The structure was refined over 18 parameters to Rwp=12.6%, Rp=10.9%, Rexp=5.03%, and RB=3.27% from 40 independent reflections. (NH4)2KWO3F3 was transformed upon cooling to a ferroelastic monoclinic phase with space group P21/n, a′=6.3072(3) Å, b′=6.3028(3) Å, c′=8.9882(3) Å, β′=90.242(2)°, V=357.30(3) Å3, Z=2, and Dx=3.383 g/cm3. The low-temperature structure at 113 K was refined over 28 parameters to Rwp=20.9%, Rp=21.3%, Rexp=12.5%, and RB=6.93% from 453 independent reflections.

Keywords

structure determinationRietveld analysispowder diffractionphase transitionoxyfluoride
Type
Technical Articles
Information
Powder Diffraction , Volume 22 , Issue 3 , September 2007 , pp. 227 - 230
Copyright
Copyright © Cambridge University Press 2007

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

Brandenburg, K. and Putz, H. (2005). DIAMOND-Crystal and Molecular Structure Visualization (computer software), Crystal Impact, Bonn, Germany.Google Scholar
Favre-Nicolin, V. and Cerný, R. (2002). “FOX, ‘free objects for crystallography’: a modular approach to ab initio structure determination from powder diffraction, ” J. Appl. Crystallogr.JACGAR10.1107/S0021889802015236 35, 734–743.CrossRefGoogle Scholar
Flerov, I. N., Gorev, M. V., Aleksandrov, K. S., Tressaud, A., Grannec, J., and Couzi, M. (1998). “Phase transition in elpasolities (ordered perovskites), ” Mater. Sci. Eng., R.MIGIEA10.1016/S0927-796X(98)00015-1 24, 81–151.CrossRefGoogle Scholar
Flerov, I. N., Gorev, M. V., Fokina, V. D., Bovina, A. F., Molokeev, M. S., Boĭko, Y. V., Voronov, V. N., and Kocharova, A. G. (2006). “Structural phase transition in elpasolite-like (NH4)2KWO3F3, ” Phys. Solid StatePSOSED 48, 106–112.CrossRefGoogle Scholar
Ravez, J., Peraudeau, G., Arend, H., Abrahams, S. C., and Hagenmuller, P. (1980). “A new family of ferroelectric materials with composition A 2B MO3F3 (A, B=K, Rb, Cs, for r A⩾r B and M=Mo, W), ” FerroelectricsFEROA8 26, 767–769.CrossRefGoogle Scholar
Rodríguez-Carvajal, J. (1997). “Fullprof, Program for Rietveld refinement, ” Laboratories Léon Brillouin (CEA-CNRS), Saclay, France.Google Scholar
Udovenko, A. A., Laptash, N. M., and Maslenikova, I. G. (2003). “Orientation disorder in ammonium elpasolites, ” J. Fluorine Chem.JFLCAR 124, 5–15.CrossRefGoogle Scholar
Visser, J. W. (1969). “A fully automatic program for finding the unit cell from powder data, ” J. Appl. Crystallogr.JACGAR10.1107/S0021889869006649 2, 89–95.CrossRefGoogle Scholar