Effective enhancement of the yellow emission of Dy3+: Na5Lu9F32 fluoride single crystal by co-doping with Tb3+ ions

Abstract

Bulk Na₅Lu₉F₃₂ (NLF) single crystals doped with 0.5 mol% Dy³⁺ and χ Tb³⁺ (χ = 0, 0.5, 1.0, 2.0, and 3.0 mol%, respectively) ions were synthesized successfully via Bridgman method. The Dy³⁺/Tb³⁺ co-doped Na₅Lu₉F₃₂ crystal structure was investigated by using X-ray diffraction (XRD) and Rietveld refinements, confirming that the Lu³⁺ sites in the crystal were successfully substituted by Dy³⁺ and Tb³⁺ ions. The fluorescence spectra of the doped NLF single crystals were investigated under excitation with 453 nm light. It was found that the intensity of the 573 nm yellow emission can be increased to about 132 % through co-doping of 1mol% Tb³⁺ ion. The energy transfer efficiency (ETE) from Dy³⁺ to Tb³⁺ was calculated, which effectively reduces the lifetime of Dy³⁺: ⁶H_13/2 energy level. The depopulation of energy level by energy transfer from ⁶H_13/2 of Dy³⁺ to ⁷F₄ of Tb³⁺ ions mainly accounts for the enhancement of the yellow emission. The results suggest that the Dy³⁺/Tb³⁺ co-doped NLF single crystal is a prospective candidate for yellow solid-state laser material in related optical device.