Eu3+-Tb3+-Tm3+ co-doped oxyfluoride glass with high quantum yield for a robust white LED color converter

BaF2-Al2O3-B2O3-SiO2 glasses and glass-ceramics doped with Eu3+-Tb3+ were fabricated as an inorganic color converter for white LEDs. The BaF2-Al2O3-B2O3 glass composition was modified by adding SiO2, and thermal and mechanical stability improved with increasing SiO2 content while maintaining a quantum yield (QY) as high as 91%. To realize white color coordinates, Tm3+ was additionally introduced at varying contents, and Eu3+ content was also controlled. Excellent chromatic properties, such as a pure white color coordinates (x = 0.33, y = 0.33) with a co-related color temperature of 5772K, and a color rendering index (CRI) of 91 under 370 nm excitation, were successfully achieved. After the glass was heat-treated at 600 C to fabricate a glass ceramic, the glass-ceramics were mounted on top of a 370 nm UV-LED, successfully demonstrating a white LED with nearly pure white color coordinates and a high CRI of 86. The increased emission intensity in the glass-ceramic was attributed to the formation of BaF2 crystals which were investigated by X-ray diffractometer (XRD) and a transmission electron microscope with energy dispersive spectroscopy (TEM-EDS).