Crystal structure of LiLnW2O8 (Ln=lanthanides and Y): An X-ray powder diffraction study

Crystal structures that occur in LiLnW2O8 (Ln=lanthanides and Y) have been studied using Rietveld profile analysis of X-ray diffraction data. Two types of structures were observed. The scheelite structure of the space group I41/a is adopted for compounds containing large lanthanides Ln=La-Gd. For smaller lanthanides (Ln=Dy-Lu and Y) the wolframite structure with the space group P2/n is observed. In LiTbW2O8, both structures occur. The phase transition between the two is a slow process making the obtainment of pure low temperature phase (wolframite) difficult. The space groups P1-bar and P2, recently reported for LiEuW2O8 and LiYW2O8, have not been observed in this series of compounds. - Graphical abstract: Part of the X-ray diffraction patterns of LiSmW2O8 and LiDyW2O8 representing two structure types in LiLnW2O8: the scheelite with Ln=La-Gd and wolframite with Ln=Dy-Lu and Y. In LiTbW2O8 both the scheelite and the wolframite structures occur at high and low temperatures, respectively. Highlights: → Double tungstates of the formula LiLnW2O8 (Ln=lanthanides and Y) were systematically synthesised and their crystal structures were determined. → LiLnW2O8 adopt either the scheelite structure (I41/a) (Ln=La-Gd) or wolframite structure (P2/n) (Ln=Dy-Lu and Y). → Both structures occur in LiTbW2O8 and the I41/a→P2/n phase transition is a slow process. → The space groups P1-bar and P2 recently reported for LiEuW2O8 and LiYW2O8 were not observed.