Dense Yttria Phase Eclipsing the A-Type Sesquioxide Structure: High-Pressure Experiments and ab initio Calculations

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• 作者：Hitoshi Yusa ; Taku Tsuchiya ; Nagayoshi Sata ; Yasuo Ohishi
• 刊名：Inorganic Chemistry
• 出版年：2010
• 出版时间：May 17, 2010
• 年：2010
• 卷：49
• 期：10
• 页码：4478-4485
• 全文大小：966K
• 年卷期：v.49,no.10(May 17, 2010)
• ISSN：1520-510X

文摘

In situ X-ray diffraction experiments and ab initio calculations elucidated the high-pressure phase transition properties of yttrium sesquioxides. The C-, B-, and A-type sesquioxides structure sequence observed in the room-temperature compression does not coincide with the high-pressure phase sequence of yttrium sesquioxides at high temperature. A reconstructive-type transformation taking place at high temperature yields the Gd₂S₃ structure around 8 GPa with a drastic change in cation-oxygen coordinations. Ab initio structural optimization suggests that a displacive-type transformation from B- to A-type sesquioxides structure metastably occurs under pressure at room temperature. The calculated density of states indicates that the transition to the Gd₂S₃ structure causes a significant decrease in the band gap. The Gd₂S₃ phase was also found to be partially recovered at ambient pressure. We briefly discuss the quenchability of the Gd₂S₃ structure in sesquioxides on the basis of the enthalpy differences between the ambient phase and the recovered products.