0000000000377229
AUTHOR
Thorsten M. Gesing
Elucidating structural order and disorder phenomena in mullite-type Al4B2O9 by automated electron diffraction tomography
The crystal structure and disorder phenomena of Al4B2O9, an aluminum borate from the mullite-type family, were studied using automated diffraction tomography (ADT), a recently established method for collection and analysis of electron diffraction data. Al4B2O9, prepared by sol-gel approach, crystallizes in the monoclinic space group C2/m. The ab initio structure determination based on three-dimensional electron diffraction data from single ordered crystals reveals that edge-connected AlO6 octahedra expanding along the b axis constitute the backbone. The ordered structure (A) was confirmed by TEM and HAADF-STEM images. Furthermore, disordered crystals with diffuse scattering along the b axis…
An average structure model of the intermediate phase between sodalite and cancrinite
Abstract Powder samples of the intermediate phase between sodalite and cancrinite (INT) have been synthesized hydrothermally. The formation of the INT phase was proved by both PXRD and TGA analysis and its stoichiometric composition was found to be |Na6.95(1)(CO3)0.48(2) (H2O)6.18(6)|[AlSiO4]6. The comparison of the intensity ratios of PXRD data with a SCXRD measurement indicates the formation of a comparable phase with the typical strong stacking disorder. The hexagonal lattice parameters with a=1266.3(2) pm and c=1586(1) pm and the unit cell setting were determined by Pawley fits. The average lattice and the stacking disorder along c axis could be confirmed by the reconstruction of three-…