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

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.

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