Crystal Structure Determination Of New Compounds Li6mb3o9 (M= Nd, Sm, Eu, Tm, Er)

New compounds Li6MB3O9 (M=Nd,Sm,Eu,Tm,Er) were synthesized by solid-state reaction. The crystal structure of Li6NdB3O9 was analyzed from both powder and single crystal X-ray diffraction data. The results obtained by powder diffraction analysis and Rietveld refinement are a=7.2725(4) angstrom, b=16.6398(9) angstrom, c=6.7529(5) angstrom, beta=105.398(8)degrees, and space group P2(1)/c, which agree with the results obtained by single crystal diffraction analysis: a=7.2712(4) angstrom, b = 16.6268 (9) angstrom, c = 6.7484(4) angstrom, beta=105.411 (1)degrees, and space group P2(1)/c. This compound is isostructural with Li6YB3O9, Single crystal structure analysis showed that the fundamental building unit of these isostructural compounds comprises three isolated [BO3](3-) triangles, one distorted [NdO8](13-) triangulated dodecahedron, four distorted [LiO5](9-) five-coordinated polyhedra, and two [LiO4](7-) tetrahedron. An analysis of the infrared spectrum of Li6NdB3O9 confirmed the presence of isolated [BO3](3-) triangles in Li6NdB3O9. The remaining four Li6MB3O9 (M=Nd, Sm, Eu, Tm, and Er) compounds were found to be isostructural with Li6NdB3O9. Their unit cell dimensions decrease with an increase in the atomic number of the rare-earth atoms. DTA and TGA measurements of Li6MB3O9 (M=Nd, Sm, Eu, Tm, and Er) revealed that these borates congruently melt from 800 degrees C to 860 degrees C. (c) 2008 International Centre for Diffraction Data.