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Structure Determination and Relative Properties of Novel Cubic Borates MM‘4(BO3)3 (M = Li, M‘ = Sr; M = Na, M‘ = Sr, Ba)
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posted on 2005-09-05, 00:00 authored by L. Wu, X. L. Chen, H. Li, M. He, Y. P. Xu, X. Z. LiA series of novel borates, MM‘4(BO3)3 (M = Li, M‘ = Sr; M = Na, M‘ = Sr, Ba), have been successfully synthesized
by standard solid-state reaction. The crystal structures have been determined from powder X-ray diffraction data.
They crystallize in the cubic space group Ia3̄d with large lattice parameters: a = 14.95066(5) Å for LiSr4(BO3)3,
a = 15.14629(6) Å for NaSr4(BO3)3, and a = 15.80719(8) Å for NaBa4(BO3)3. The structure was built up from 64
small cubic grids, in which the M‘ atoms took up the corner angle and the BO3 triangles or MO6 cubic octahedra
filled in the interspaces. The isolated [BO3]3- anionic groups are perpendicular to each other, distributed along
three 〈100〉 directions. The anisotropic polarizations were counteracting, forming an isotropic crystal. Sr and Ba
atoms were found to be completely soluble in the solid solution NaSr4-xBax(BO3)3 (0 ≤ x ≤ 4). The
photoluminescence of samples doped with the ions Eu2+ and Eu3+ was studied, and effective yellow and red
emission was detected, respectively. The results are consistent with the crystallographic study. The DTA and TGA
curves of them show that they are chemically stable and congruent melting compounds.