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? and P2, recently reported for LiEuW₂O₈ and LiYW₂O₈, have not been observed in this series of compounds.