Abnormal positive thermal expansion in Mo substituted ZrW2O8

作者：Liu, Qinqin^*; Yang, Juan; Cheng, Xiaonong; Sun, Xiujuan; Zang, Chuanliang

来源：Physica B: Condensed Matter , 2011, 406(18): 3458-3464.

DOI：10.1016/j.physb.2011.06.024

• Mo substitution
• Abnormal positive thermal expansion property
• Zr2-xMoxO8

ZrW2O8 displays the unusual property of an isotropic bulk contraction in volume as a function of temperature. We report here on the positive thermal expansion (PTE) property caused by substituting Mo for W sites in ZrW2O8 at room temperature. The room temperature crystal structure of ZrW2-xMoxO8 compounds, which were synthesized using a low temperature route, could be divided into ordered phase with alpha-ZrW2O8 structure (0 <= x <= 0.5) and disordered phase with beta-ZrW2O8 (0.5 <= x <= 1.5) and c-ZrMo2O8 structure (1.5 <= x <= 2). ZrW2-xMoxO8 adopting beta-ZrW2O8 structure shows abnormal PTE property at room temperature due to the existence of water molecules, while ZrW2-xMoxO8 adopting the other two structures (alpha-ZrW2O8 and c-ZrMo2O8) shows negative thermal expansion (NTE) property from room temperature until decomposition for alpha-ZrW2O8 structure or trigonal phase transition for c-ZrMo2O8 structure. The reason lies in the fact that the oxygen migration caused by the Mo substitution leads to the re-arrangement of W(Mo)O-4 tetrahedra lying along the 3-fold axis, only particular W/Mo ratio (0.5 <= x <= 1.5) produces a special crystal structure, which allows the entrance of water molecules.

• 出版日期2011-9-15
• 单位江苏大学