Structure of 未-Alumina: Toward the Atomic Level Understanding of Transition Alumina Phases

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• 作者：Libor Kovarik ; Mark Bowden ; Arda Genc ; J谩nos Szanyi ; Charles H. F. Peden ; Ja Hun Kwak
• 刊名：Journal of Physical Chemistry C
• 出版年：2014
• 出版时间：August 7, 2014
• 年：2014
• 卷：118
• 期：31
• 页码：18051-18058
• 全文大小：478K
• ISSN：1932-7455

文摘

Transition Al₂O₃ derived from thermal decomposition of AlOOH Boehmite have complex structures and to a large extent remain poorly understood. Here, we report a detailed atomic level analysis of 未-Al₂O₃ for the first time using a combination of high-angle annular dark field electron microscopy imaging, X-ray diffraction refinement, and density functional theory calculations. We show that the structure of 未-Al₂O₃ represents a complex structural intergrowth from two main crystallographic variants, which are identified as 未₁-Al₂O₃ and 未₂-Al₂O₃. The two main variants are fully structurally described, and in addition, we also derive their energy of formation. On the basis of comparison with other relevant transition Al₂O₃ phases, it is shown how energetic degeneracy leads to the structural disorder and complex intergrowths among several transition Al₂O₃. The results of the work have important implications for understanding thermodynamic stability and transformation processes in transition alumina.