Upconversion Luminescence and Color Tunability Properties in Tm3+-Ho3+-Yb3+ Co-Doped Oxyfluoride Nano-Glass-Ceramics

Transparent oxyfluoride nano-glass-ceramics with highly efficient up-conversion and adjustable color luminescence were developed in the 50SiO₂-15AlF₃-10BaF₂-15PbF₂-(9.3-x)GdF₃ -0.5YbF₃-0.2TmF₃-xHoF₃ (x = 0.02, 0.05, 0.10, 0.50)composition in mol%. X-ray diffraction measurements revealed that heat treatments of the oxyfluoride glasses cause the precipitation of rare-earth ions co-doped fluorite-type of β-PbF₂ in the glass matrix. Under 980 nm laser excitation, intense red, green and blue up-conversion luminescences were simultaneously observed in these transparent nanoglass-ceramics owing to the successive energy transfer from Yb³⁺ to Ho³⁺ and Tm³⁺ ions. Various colors of luminescence, including bright perfect white light, can be tuned by adjusting the concentrations of the Ho³⁺ ions in the material. A possible energy transfer process and up-conversion luminescence mechanism in the nano-glass-ceramics are proposed and discussed.