Hygroscopicity, phase transition and thermal expansion in Yb2-xGaxW3O12 system

Abstract

This study indicates that highly hygroscopic Yb2W3O12 adopts a monoclinic system at room temperature and atmospheric conditions, influenced by the presence of water molecules within the crystal framework. It seems that only after the complete dehydration at ∼100 °C, a monoclinic-to-orthorhombic transition occurs.The same water effect on the crystal system was observed in the Yb2-xGaxW3O12 series, ranging from 0.2 to 0.5. Yb3+ fluorescence emission band of Yb2-xGaxW3O12 is severely reduced in more hygroscopic phases. As the amount of Ga3+ increases in the Yb2-xGaxW3O12, coefficient of thermal expansion (CTE) becomes less negative, whereas the Yb3+ luminescence increases due to a less hygroscopic environment.