Compositional dependence of Judd-Ofelt parameters ofEr3+ions in alkali-metal borate glasses

Abstract
The Judd-Ofelt intensity parameters, Ωt (t=2,4,6) for f-f transitions of Er3+ ions doped in B2 O3-R2O (R=Na,K) glasses were determined from optical-absorption measurements, and their compositional dependence was investigated systematically. The values of Ω2 exhibited a maximum around 25 mol % R2O, while those of Ω4 and Ω6 decreased monotonically with an increase in R2O content. The compositional dependences of Ω4,6 were consistent with those of the isomer shift in Eu151 Mössbauer spectroscopy, which gives information about the 6s-electron density of Eu3+ ions. The variation of Ω2 against R2O content was related to the change in asymmetry of the rare-earth ligand due to the structural mixing of borate groups, while those of Ω4,6 were related to the local basicity of rare-earth sites in the glass.

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