Crystal structure of the metastable form of aluminum trifluoride β-AlF3 and the gallium and indium homologs
1988; Elsevier BV; Volume: 77; Issue: 1 Linguagem: Inglês
10.1016/0022-4596(88)90095-3
ISSN1095-726X
AutoresA. Le Bail, C. Jacoboni, M. Leblanc, R. De Pape, H. Duroy, J.L. Fourquet,
Tópico(s)Luminescence Properties of Advanced Materials
ResumoThe crystal structure of the metastable phase β-AlF3, which is related to the hexagonal tungsten bronze structure, has been solved by X-ray powder and single-crystal diffraction methods. The crystal habit is pseudo-hexagonal with systematic twinning (rotation of 120° around the c axis), but the true symmetry is orthorhombic with space group Cmcm, Z = 12, a = 6.931(3), b = 12.002(6), c = 7.134(2), Å (R = 0.044 and Rw = 0.051) from 929 independent reflections). The network is built from very regular AlF6 octahedra rotated by approximately 7.2° from the positions of the ideal HTB structure. A similar network, with the same propagation of the tilting, was observed in the compound (H2O)0.33FeF3 and in the metastable polymorphs of CrF3 and of VF3. Our reinvestigation of the structures of β-GaF3 and β-InF3 using powder data shows that they are isotypic with the aluminum compound, with a = 7.210(1), b = 12.398(2), c = 7.333(1) and a = 7.875(2), b = 13.499(4), c = 7.956(2), Å, respectively.
Referência(s)