COMPOSITIONAL DEPENDENCE OF JUDD-OFELT PARAMETERS OF ER3+ IONS IN ALKALI-METAL BORATE GLASSES

The Judd-Ofelt intensity parameters, OMEGA(t), (t = 2,4,6) for f-f transitions of Er3+ ions doped in B2O3-R2O (R = Na,K) glasses were determined from optical-absorption measurements, and their compositional dependence was investigated systematically. The values Of OMEGA-2 exhibited a maximum around 25 mol % R2O, while those of OMEGA-4 and OMEGA-6 decreased monotonically with an increase in R2O content. The compositional dependences Of OMEGA-4,6 were consistent with those of the isomer shift in Eu-151 Mossbauer spectroscopy, which gives information about the 6s-electron density of Eu3+ ions. The variation Of OMEGA-2 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 OMEGA-4,6 Were related to the local basicity of rare-earth sites in the glass.