||In this study, a sol-gel method is used to enhance the fluorescence intensity of the glass phosphor and reduce the problem of impurity diffusion inside the glass. Firstly, the Ce3+:YAG powder was coated with SiO2 nano thin film. The coated Ce3+:YAG powder was mixed uniformly with low temperature glass powder and sintered at 700℃. The glass phosphor is named as sol-gel Ce3+:YAG doped glass (SGCeYDG).|
According to the Fresnel transmission theory, the transmittance of Ce3+:YAG powder coated with SiO2 nano film was 5% higher than Ce3+:YAG powder without coated. Owing to the total internal reflection angle increasing (33°→43°), the total internal reflection of fluorescence will be reduced. A intergrating sphere and a fluorescence spectrometer were employed to measure the quantum efficiency and fluorescence intensity of glass phosphor. In comparison with Ce3+:YAG doped glass (CeYDG) without coated SiO2, the quantum efficiency and fluorescence intensity of SGCeYDG was improved about 3.95% and 6.58%, respectively.
To verify the micro-structure and composition of SiO2 film, SEM, EDS, FTIR and HRTEM were employed. Furthermore, high temperature accelerated aging test and damp heat test were used to compare the reliability between SGCeYDG, CeYDG and Ce3+:YAG doped silicone (CeYDS). In the reliability test parts, the high temperature accelerated aging test (HTAAT) and damp heat test (DHT) were used to compare the reliability between SGCeYDG, CeYDG and CeYDS. At the HTAAT-450℃, the CeYDS has been carbonized. The lumen loss of SGCeYDG and CeYDG were about 3% and 7%, respectively. The color drift of SGCeYDG and CeYDG were about 5.5×10-3 and 9.6%×10-3, respectively. On the other hand, After the DHT, The lumen loss of SGCeYDG, CeYDG and CeYDS were about 3.35%, 5.07% and 6.81%, respectively. The color shift of SGCeYDG, CeYDG and CeYDS were about 0.69×10-3, 1.31×10-3 and 6.81×10-3, respectively. The results of reliability test exhibited that the lumen loss and color drift of SGCeYDG were lower than CeYDG and CeYDS. Therefore, the SGCeYDG has the potential to apply to develop as the phosphor of high power white LED as its good heat-resistance and moisture-resistance.