Intense Ultraviolet and Blue Upconverison Emissions in Tb³⁺/Yb³⁺ Codoped KY₃F₁₀ Nanocrystals

Tb 3+ /Yb 3+ codoped KY 3 F 10 nanocrystals with the average size of 45 nm were synthesized using a facile hydrothermal method. Under the excitation by a 976 nm laser, the codoped samples exhibited intense ultraviolet ( 5 D 3 → 7 F 6 ) and blue upconversion emissions ( 5 D 3 → 7 F 5 ) from Tb 3+ ions. It was observed for the first time that the intense ultraviolet emission was two times stronger than the green emission of Tb 3+ , which was about 100 times stronger than the results previously reported. The upconversion mechanism was investigated based on the energy transfer from Yb 3+ to Tb 3+ and the cross-relaxation process between Tb 3+ pairs.