Eu2+-doped oxyfluoride glass-ceramic with nepheline as an efficient 400 nm UV-LED color converter

SiO2-Na2O-Al2O3-LaF3 glass-ceramics doped with Eu2+ were synthesized as an efficient inorganic color converter for 400 nm UV-LED. When Eu2+ formed within the glass matrix, the obtained glass showed cyan emission under 400 nm excitation, but its emission peak drastically shifted to greenish yellow upon heat treatment. With heat treatment the glass-ceramic also showed highly increased emission intensity, and the color coordinate of the glass-ceramic shifted to yellow. When it was mounted on top of a 400 nm UV-LED, it demonstrated high color conversion efficiency and practical feasibility as an UV-LED color converter. To vary the color coordination the heat-treatment conditions and the thickness of the glass-ceramic were adjusted. The resulting ceramic showed a high quantum yield of up to 78%, which is comparable to conventional ceramic phosphors. The spectral change in the glass-ceramic is attributed to the formation of nepheline and LaF3 crystalline phases. X-ray diffractometer (XRD), transmission electron microscope with energy dispervise spectroscopy (TEM-EDS) and cathode luminescence (CL) were used to investigate the mechanism of Eu2+-doped nepheline crystal formation, and its effect on the spectral change with heat treatment.

Automated summary

The SiO2-Na2O-Al2O3-LaF3 glass-ceramics doped with Eu2+ exhibit efficient color conversion for 400 nm UV-LED, with cyan emission shifting to greenish yellow after heat treatment. The heat-treated glass-ceramic shows increased emission intensity and shifts in color coordination. By adjusting heat-treatment conditions and thickness, the color coordination can be varied.