Real-Space Distribution of Local WO4 Ordering in Negative Thermal Expansive ZrW2O8

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• 作者：Yukio Sato ; Yasuhisa Yamamura ; Kazuya Saito ; Yuichi Ikuhara
• 刊名：The Journal of the American Chemical Society
• 出版年：2012
• 出版时间：August 29, 2012
• 年：2012
• 卷：134
• 期：34
• 页码：13942-13945
• 全文大小：316K
• 年卷期：v.134,no.34(August 29, 2012)
• ISSN：1520-5126

文摘

Solids usually expand when they are heated. This is quite common behavior of solids; however, there are some exceptions. Zirconium tungstate (ZrW₂O₈) is a prototype material among them, because it has the highest degree of negative thermal expansion (NTE) over broad temperature range. Intensive investigation of NTE mechanisms has suggested the importance of metal鈥搊xygen polyhedra. However, most of the studies have been done with volume-averaged techniques, and microscopic information has been lacking. Here, our electron microscopy observations have unraveled the real-space distribution of local WO₄ tetrahedra ordering for the first time. We have found that (i) the WO₄ ordering is partly inverted; (ii) WO₄ is disordered on the nanoscale; and (iii) doping with scandium enhances the WO₄ disordering. These findings led to construction of a microstructure model for ZrW₂O₈, providing a new structural perspective for better understanding of local structure and its role in phase transitions.