Atomistic Observation of Phase Transitions in Calcium Sulfates under Electron Irradiation

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• 作者：Fan Cao ; He Zheng ; Shuangfeng Jia ; Xueshi Bai ; Lei Li ; Huaping Sheng ; Shujing Wu ; Wei Han ; Minmin Li ; Guangyu Wen ; Jin Yu ; Jianbo Wang
• 刊名：Journal of Physical Chemistry C
• 出版年：2015
• 出版时间：September 24, 2015
• 年：2015
• 卷：119
• 期：38
• 页码：22244-22248
• 全文大小：494K
• ISSN：1932-7455

文摘

The detailed study of phase transition processes among various calcium sulfates is still insufficient in spite of its importance in artificial and natural processes. Here, the phase transformation 纬-CaSO₄ 鈫?尾-CaSO₄ 鈫?CaO is induced by electron beam irradiation and directly observed inside the transmission electron microscope (TEM). Relying on the real-time atomic-scale observation, the topological transition from 纬-CaSO₄ (hexagonal) to 尾-CaSO₄ (orthorhombic) is investigated in detail, and the orientation relationship is determined: [0001]_H//[001]_O and (101虆0)_H//(010)_O. Furthermore, three 尾-CaSO₄ variants related by 120掳 rotation are observed, which is theorized to occur during the transformation from hexagonal to orthorhombic structure. The possible transition mechanism is thus discussed. This work offers detailed information on the transition mechanism concerning the calcium sulfates, which might facilitate their industrial applications and possibly further understanding of rock deformation in the earth crust.