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|Type:||Artigo de periódico|
|Title:||Exafs Investigation Of Local Structure Of Er3+ And Yb 3+ In Low-silica Calcium Aluminate Glasses|
|Abstract:||Erbium and ytterbium environments in low-silica calcium aluminate glasses, with nominal composition 58 CaO, 27.1-x Al2O3, 6.9 MgO, 8 SiO2, xcEr2O3, OrYb2O3, 0.2≤x=≤1.5 (mol%), were investigated using x-ray-absorption fine-structure spectroscopy (EXAFS) on the Er and Yb LIII edge. The average Er-O bond separation was found to vary only slightly between 2.24 and 2.21 Å and the Yb-O bond between 2.20 and 2.18 Å. The first-shell coordination number decreased as the rare-earth oxide replaced Al2O3. For Er2O3-doped samples this decrease was about 28%, from 6.5 to 4.7 atoms, whereas for Yb2O3-doped ones it was about 14%, from 6.4 to 5.5 atoms. The decrease in the coordination number is attributed to the difficulty of rare-earth atoms to coordinate a larger number of the nonbridging oxygens that appear as the CaO/Al2O3 ratio decreases. The Debye-Waller factor 2σ2 varied from 0.026 to 0.012 Å2.|
|Appears in Collections:||Unicamp - Artigos e Outros Documentos|
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