Phase Transformation and Negative Thermal Expansion in TaVO5

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• 作者：Xiaowei Wang ; Qingzhen Huang ; Jinxia Deng ; Ranbo Yu ; Jun Chen ; Xianran Xing
• 刊名：Inorganic Chemistry
• 出版年：2011
• 出版时间：March 21, 2011
• 年：2011
• 卷：50
• 期：6
• 页码：2685-2690
• 全文大小：884K
• 年卷期：v.50,no.6(March 21, 2011)
• ISSN：1520-510X

文摘

Two phase transformations of TaVO₅ were observed by DSC and/or dilatometry measurements in the studied temperature range. X-ray diffraction and neutron powder diffraction structure refinements indicated a phase transformation at 鈭?4 掳C from a monoclinic symmetry with space group P2₁/c to an orthorhombic symmetry with space group Pnma above this temperature. The rigid TaO₆ octahedron in orthorhombic phase becomes nonregular at 鈭?4 掳C, which results in the transition from Pnma to P2₁/c. TaVO₅ was found to be a negative thermal expansion material above room temperature. The calculated volumetric thermal expansion coefficients (TECs) are 鈭?.92 脳 10^鈭? 掳C^鈭? in the range of 20鈭?00 掳C, and 鈭?.19 脳 10^鈭? 掳C^鈭? above 600 掳C, respectively. The negative thermal expansion behavior is accounted for by the tilt of the TaO₆ and VO₄ polyhedra, where the shrinkage of the VO₄ tetrahedra result in the increase of Ta鈭扥鈭扸 angles on heating, while the angle of Ta鈭扥1鈭扵a maintains at 180掳 in the framework.