Crystal structure of Li LnW 2O 8 ( Ln=lanthanides and Y): An X-ray powder diffraction study

Abstract

Crystal structures that occur in Li LnW 2O 8 ( 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 I4 1/ 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 LiTbW 2O 8, 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 P1̄ and P2, recently reported for LiEuW 2O 8 and LiYW 2O 8, have not been observed in this series of compounds.