Year: 2019
Type: article
Abstract: Metastable polymorphs of Al 2 O 3 accommodate a large amount of structural disorder that has proven difficult to quantify. In the case of δ-Al 2 O 3, the nature of crystallographic disorder has recently started to emerge as a planar structural intergrowth. In this work, which uses aberration-corrected high-angle annular dark-field scanning transmission electron microscopy imaging and ab initio calculations, we reveal a new type of structural intergrowth in δ-Al 2 O 3 and show that it is an important part of the complex/defected δ-Al 2 O 3 microstructure. The newly identified intergrowth is different from the previously known type due to intergrowth direction and variant selection. In its most basic representation, the new intergrowth consists of three variants of δ 2 -Al 2 O 3, δ 3 -Al 2 O 3, and δ 4 -Al 2 O 3 . As a part of this work, we derive the crystallography and structural relationship between the variants and discuss the overall crystallography of δ-Al 2 O 3 in the context of previous structural interpretations. Finally, it is shown that the individual δ-Al 2 O 3 variants can be related to other metastable polymorphs that are known to evolve from γ-Al 2 O 3 .
Language: English
Subfield: Structural Biology
Domain: Life Sciences
Open Access status: green
Award: G5692233181
OpenAlex ID: W2923692196