Microstructural Analysis of a Negative Thermal Expansion Material ZrW₂O₈

Yukio Sato^a, Yasuhisa Yamamura^b and Yuichi Ikuhara^c

^aDepartment of Materials Science and Engineering, Graduate School of Engineering, Kyushu University
^bFaculty of Pure and Applied Sciences, University of Tsukuba
^cInstitute of Engineering Innovation, The University of Tokyo

Abstract: Zirconium tungstate (ZrW₂O₈) exhibits negative coefficient of thermal expansion, which is not the case for most materials. It is believed that the negative thermal expansion should be closely related with geometrical alignment of WO₄ tetrahedra in ZrW₂O₈. In this article, we introduce our recent study that revealed the spatial distribution of WO₄ geometrical ordering state using dark-field transmission electron microscopy. It was found that the WO₄ geometrical ordering is partly inverted and is partly disordered on the nanoscale.

Key words: ZrW₂O₈, Negative Thermal Expansion, Dark-Field, TEM, Electron Diffraction