Research On Growth And Performance Of YAG:Ce³⁺-Al₂O₃ Eutectic Fluorescent Material In Wled By Hds Method

White LED(WLED for short) has gradually emerging in the field of lighting for its long service life, high luminous efficiency and environmental pollution-free advantages.At present, the main realization form of commercialization of white LED is a blue chip combined with YAG:Ce3+yellow phosphor, but poor thermal conductivity of phosphor and the difficult of heat dissipation, have easily resulted in the decrease of the light conversion efficiency of phosphor and then reduce the LED luminous efficiency and a series of problems. In order to solve the above problems, this subject adopts horizontal directional solidification growth YAG:Ce3+-Al2O3 eutectic ceramics instead of YAG:Ce3+phosphors.With the method of horizontal directional solidification, a growth method of single crystal, we have grown a YAG:Ce3+-Al2O3 eutectic ceramic with the size of 147 mm x150 mm x 10 mm, and then carried on the performance testing of the eutectic ceramics.After that we analyzed its feasibility of substituting the YAG:Ce3+phosphor, and provided reference opinions to find the best parameters of eutectic ceramic packaging white LED.YAG:Ce3+-Al2O3 eutectic ceramics were analyzed by XRD and SEM. the test results show that the eutectic contains only two phase YAG and Al2O3, and two phase alternates irregularly growth throughout the whole eutectic ceramics to form a three-dimensional network architecture. XPS analysis was carried out on the eutectic ceramics, and we found that Ce ions have fully translated into the Ce3+ in the eutectic ceramics. We also found that Ce ion valence did not change before and after two hours’ annealing at 1000oC. Vickers hardness of the eutectic ceramics have been measured at15.6 GPa,but high hardness increases the the difficulty of eutectic ceramic packing into LED. The eutectic ceramics was tested by atomic force microscopy of roughness before and after polishing. Due to the roughness affecting light absorption efficiency of eutectic ceramics piece, therefore appropriately polishing can improve the luminous performance of white LED. We tested the eutectic ceramics’ excitation spectrum and emission spectrum, and found that there are two peaks in the excitation spectrum respectively at 345 nm and 470 nm. Both peaks are in the blue band excitation and the peak at 470 nm is stronger.With a exciting blue light of wavelength 455 nm, we got an emission spectrum, emission range between 485 nm to 670 nm, center wavelength of555 nm in the orange light band, and the center of the emission wavelength keep constant with the change of temperature. Excitation spectrum and emission spectrum match well. The quantum efficiency test results showed that the quantum efficiency of eutectic ceramic increases with the reduction of eutectic ceramic chip thickness; The quantum efficiency of Eutectic ceramic packing LED is markedly lower than the quantum efficiency of fluorescence silicon sheet enclosed LED because of the Ce doping amount of eutectic ceramic is too high. The eutectic ceramic packaging LED light electric parameter test results show that the luminous efficiency of eutectic ceramics piece packaging LED increases with the decrease of the thickness of eutectic ceramics piece, but less than that of the fluorescent powder silica encapsulation packaging LED. The reason is the same to smaller of quantum efficiency; Eutectic ceramic chip encapsulation of LED color coordinate, color temperature and color rendering index are better than the fluorescent powder silica encapsulation of LED,and to a certain extent, thinning eutectic ceramic chip thickness can improve the LED light color performance, such as color coordinates, color temperature, color rendering index etc.