Structure of new perovskite-related compounds, LiCuM3O9(M = Nb, Ta)

Abstract

The structure of newly prepared LiCuM₃O₉(M = Nb, Ta) has been determined from the powder X-ray diffraction pattern. The Rietveld refinement confirms that the compounds adopt a distorted perovskite structure [a= 7.5286(1)Å with I23 space group for M = Nb and a= 7.5178(1)Å with Im for M = Ta], which is compatible with that of CuTa₂O₆. Li and Cu atoms are statistically distributed over the A sites with equimolar ratio in the manner of an almost square-planar coordination, the total occupancy of which is 8/9.