Crystal Structure of 尾-Fe2O3 and Topotactic Phase Transformation to 伪-Fe2O3

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• 作者：Teruaki Danno ; Daisuke Nakatsuka ; Yoshihiro Kusano ; Hiroshi Asaoka ; Makoto Nakanishi ; Tatsuo Fujii ; Yasunori Ikeda ; Jun Takada
• 刊名：Crystal Growth & Design
• 出版年：2013
• 出版时间：February 6, 2013
• 年：2013
• 卷：13
• 期：2
• 页码：770-774
• 全文大小：356K
• 年卷期：v.13,no.2(February 6, 2013)
• ISSN：1528-7505

文摘

尾-Fe₂O₃ is the scarce polymorph of Fe₂O₃ phases and is transformed easily into 伪-Fe₂O₃ at high temperature. However, its crystal structure and the transformation mechanism to 伪-Fe₂O₃ are still unclear because of the difficulty in obtaining monophasic 尾-Fe₂O₃ crystals. We established a synthesis method of the monophasic 尾-Fe₂O₃. It was synthesized by a two-step reaction: heating a mixture of Na₂SO₄ and Fe₂(SO₄)₃ in air at 250 掳C to form NaFe(SO₄)₂, and subsequent heating the resultant phase with NaCl in air at 500 掳C. The crystal structure was refined to a bixbyite-type cubic structure (Ia3̅) with a = 9.4039(1) 脜 by the Rietveld method. Single crystalline 尾-Fe₂O₃ particles of approximately 1 渭m in size were topotactically transformed into single 伪-Fe₂O₃ crystals. Electron diffraction analysis revealed the crystallographic orientation relationships between 尾-Fe₂O₃ and 伪-Fe₂O₃ to be [100]_尾//[0001]_伪, [010]_尾//[101虆0]_伪, and [001]_尾//[1̅21虆0]_伪.