Real-space distribution of local WO4 ordering in negative thermal expansive ZrW2O8.
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.
Institute of Engineering Innovation, The University of Tokyo, 2-11-16 Yayoi, Bunkyo, Tokyo 113-8656, Japan. y_sato@sigma.t.u-tokyo.ac.jp
Yukio
Y
Sato
Yasuhisa
Y
Yamamura
Kazuya
K
Saito
Yuichi
Y
Ikuhara