Real-Space Distribution of Local WO(4) Ordering in Negative Thermal Expansive ZrW(2)O(8) |
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Authors: | Yukio Sato Yasuhisa Yamamura Kazuya Saito Yuichi Ikuhara |
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Institution: | Institute of Engineering Innovation, The University of Tokyo , 2-11-16 Yayoi, Bunkyo, Tokyo 113-8656, Japan. |
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Abstract: | Solids usually expand when they are heated. This is quite common behavior of solids; however, there are some exceptions. Zirconium tungstate (ZrW(2)O(8)) 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-oxygen 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 WO(4) tetrahedra ordering for the first time. We have found that (i) the WO(4) ordering is partly inverted; (ii) WO(4) is disordered on the nanoscale; and (iii) doping with scandium enhances the WO(4) disordering. These findings led to construction of a microstructure model for ZrW(2)O(8), providing a new structural perspective for better understanding of local structure and its role in phase transitions. |
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