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Thermodiffractometry and crystal structures of the hexagonal-tungsten-bronze-related K3Al3F12⋅nH2O (n=2,1)

Published online by Cambridge University Press:  29 February 2012

A. Le Bail
A. Le Bail*
Affiliation:
Laboratoire des Oxydes et Fluorures, CNRS UMR 6010, Université du Maine, Avenue O. Messiaen, 72085 Le Mans Cedex 9, France
*
a)Electronic mail: armel.le_bail@univ-lemans.fr
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Abstract

K3Al3F12⋅nH2O (n=2,1) are the successive products of the thermal decomposition of K(H3O)2AlF6. Both structures are orthorhombic, built up from disconnected hexagonal-tungsten-bronze (HTB)-related layers, with K+ cations and H2O molecules inserted between. For n=2, there are two disconnected layers along a presenting different octahedra tilting [a=13.5135(2) Å, b=7.0433(1) Å, c=12.2252(2) Å, V=1163.60(3) Å3, Z=4, space group Pnma], whereas for n=1, the stacking is reduced to only one HTB layer along c [a=7.0523(5) Å, b=12.1005(9) Å, c=6.7057(5) Å, V=572.24(7) Å3 (at 170 °C), Z=2, space group Pmmn] after the departure of one water molecule. The thermodiffractometry ends in the α-KAlF4 form.

Keywords

potassium aluminum fluoride hydratespowder diffractioncrystal structurethermodiffractometry

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Type
Technical Articles
Information
Powder Diffraction , Volume 24 , Issue 4 , December 2009, pp. 292 - 300
Copyright
Copyright © Cambridge University Press 2009

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