Spectroscopy and Calculations for f–f Transitions of Tb³⁺ Ions in KY₃F₁₀ Nanocrystal

A modified Judd–Ofelt theory is used in this paper to treat the electric dipole transitions within the 4f ⁸ configuration of Tb³⁺ by considering the main perturbing components. Through the energy-level calculation and the strandard tensorial analysis, the explicit distances between the 4f ⁷5d configuration and the ⁵D₄ state and other lower 4f ⁸ energy levels are determined. The rare-earth ion Tb³⁺ substituted at Y³⁺ sites in KY3F10 has the site symmetry of C_4v . The standard Judd–Ofelt parameters A² ₁₀, A_{2 30}, A⁴ ₃₀, A_{4 50}, A⁶ ₅₀, A⁴ ₅₄ and A⁶ ₅₄ are included in the calculation together with odd-λ parameters A¹ ₁₀, A³ ₃₀, A⁵ ₅₀ and A⁵ ₅₄. The fluorescence branching ratios originating from ⁵D₄ are calculated. Compared with the experimental measurements, the modified model yields better results than the standard Judd–Ofelt theory.