Pressure induced phase transition of nanocrystalline and bulk maghemite (γ-Fe₂O₃) to hematite (α-Fe₂O₃)

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• 作者：Hongyang Zhu ; Yanzhang Ma ; Haibin Yang ; Cheng Ji ; Dongbin Hou ; Lingyun Guo
• 关键词：C. High Pressure ; C. X-ray diffraction
• 刊名：Journal of Physics and Chemistry of Solids
• 出版年：2010
• 出版时间：August 2010
• 年：2010
• 卷：71
• 期：8
• 页码：1183-1186
• 全文大小：684 K

文摘

Phase transition and bulk moduli of bulk and nanocrystalline γ-Fe₂O₃ were studied using synchrotron X-ray diffraction under high pressure. Contrary to most other nanomaterials, nanocrystalline γ-Fe₂O₃ begins to transform into α-Fe₂O₃ at the same pressure as bulk γ-Fe₂O₃, which is caused by a special structure of γ-Fe₂O₃, in which there exist vacancies of crystal. It is believed that phase transition starts from a certain site of vacancy because of the stress concentration at vacancy sites. Compared to bulk material, nanocrystalline γ-Fe₂O₃ has a larger bulk modulus, which is ascribed to the large ratio of surface to volume.