Study of the structures and thermal expansion properties of solid solutions Yb2−xDyxW3O12 (0≤x≤1.5 and 1.8≤x≤2.0)

Here a new series of solid solutions Yb2−xDyxW3O12 (0≤x≤1.5 and 1.8≤x≤2.0) are prepared by conventional solid-state reaction. Their crystal structures and thermal expansion properties are studied using X-ray diffraction and thermal analysis. It is found that Yb2−xDyxW3O12 with 0≤x≤1.5 adopt orthorhombic structure and show a negative thermal expansion (NTE) in temperature range of 200–800 °C, with lattice parameters a, b and c all contracting as temperature increases. The substitution of dysprosium for ytterbium results in stronger NTE in Yb2−xDyxW3O12 comparing to that in Yb2W3O12. On the other hand, compounds of Yb2−xDyxW3O12 with 1.8≤x≤2.0 adopt monoclinic structure and show positive thermal expansion in the 25–800 °C range. The different crystal structures lead to the observed different thermal expansion behaviors in Yb2−xDyxW3O12. Thus, the thermal expansion properties of Yb2−xDyxW3O12 can be controlled by careful adjusting of x.