Glass crystallization makes red fluorescent material for warm white high-power light

PICTURE: (a), MgO-Al2O3-SiO2 ternary glass phase diagram showing the chemical composition of the glass in the cordierite range (chemical formula of Mg2Al4Si5O18). (b) XRD pattern of glass and glass crystallized phosphor. Wide XRD … view More

Photo credit: by Tao Hu, Lixin Ning, Yan Gao, Jianwei Qiao, Enhai Song, Zitao Chen, Yayun Zhou, Jing Wang, Maxim S. Molokeev, Yu-Chun Chuang, Xiaoxing Ke, Zhiguo Xia, and Qinyuan Zhang

High-performance solid-state lighting with laser diodes (LD) can generate a super-high luminance that exceeds the source of light-emitting diodes (LEDs) according to the state of the art by a factor of 2-10, which makes them particularly attractive for car headlights. Outdoor lighting, multimedia projectors, laser TVs and so on. While the thermal shock to the laser is extreme and, under intense laser excitation, conventional LED phosphors would suffer from luminescence degradation or even failure due to luminescence saturation. To overcome this shortcoming, highly efficient and stable luminescent phosphors including single crystal, polycrystalline ceramic phosphor and glass-ceramic composite phosphor have received enormous attention. Due to their ease of manufacture, low cost, mass production and excellent optical properties, luminescent glass ceramics are considered to be the most promising and reliable color converter for high power laser applications.

On the other hand, the routine method of building high-power lighting based on “blue laser + yellow emitting YAG: Ce3 + garnet” is flawed in applications because of the lack of a red component. However, there is no commercially available red-emitting bulk phosphor and its exploration continues to stagnate, severely limiting the advancement of high-power lighting.

In a new article published in Light Science & Application, a team of scientists led by Professor Zhiguo Xia and Professor Qinyuna Zhang of the South China University of Technology discovered an efficient Mg2Al4Si5O18: Eu2 + composite red-emitting phosphor Using Induced Heat Treatment Developed The Glass Structure Relaxation and Crystallization Method and Professor Lixin Ning of Anhui Normal University performed the theoretical calculation to support the experimental results. An intense red emission at 620 nm with a high internal / external quantum efficiency of 94.5% / 70.6% and a high thermal stability was realized under 450 nm blue light excitation. Notably, there are rare reports of the manufacture of Eu2 + -activated red-emitting glass-ceramic phosphor by a glass crystallization process. DFT calculations and EXAFS adjustments reveal the quasi-planar Eu2 + activators that are coordinated with 6 oxygen atoms on the free channel of the Mg2Al4Si5O18 crystal. Red emitting laser controlled devices constructed by coupling the phosphor to a 445 nm blue laser exhibit a high laser saturation threshold of 3.25 W mm &min; ², a high luminous flux of 274 lm and a luminous efficiency of 54 lm W & supmin; ¹, which is almost equal to the highest rank among the red bulk phosphors. The Mg2Al4Si5O18: Eu2 + composite phosphor described has the potential to overcome the shortage of commercially available purely inorganic red-emitting bulk color converters and will represent a major step in the advancement of solid-state lighting technology for new photonic applications.


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