Study On Spectral Regulation And Luminescence Properties Of Silicon-based Garnet Phosphors

Currently,the most well-known commercial white LEDs are garnet-type YAG:Ce³⁺ yellow phosphors excited by blue LEDs.Due to the lack of red light in the emission spectrum of the phosphors,the synthesized white LEDs exhibit lower color rendering index and high color temperature.In response to the above problems,Can He et al,reported Y₃MgAl₃SiO₁₂?YMAS?:Ce³⁺ phosphors,which have better performance than YAG:Ce³⁺,but the lack of red light components also leads to high color temperature?CCT=4882K?.Therefore,Y₃MgAl₃SiO₁₂ is selected as the matrix material,and the red light component in the emission spectrum is increased by doping Mn²⁺ in Y₃MgAl₃SiO₁₂:Ce³⁺,and the color temperature is lowered.In addition,the luminescence properties and energy transfer mechanism of the matrix during the synthesis of single-matrix white phosphors were investigated by single doping and co-doping of Dy³⁺ and Eu³⁺,respectively.The specific research contents and results are as follows:?1?YMAS:Ce³⁺,Mn²⁺ yellow phosphor was prepared by high-temperature solid-state reaction under a reducing atmosphere.The crystal structure related information of YMAS was determined by X-ray diffraction data and Reitveld refinement results.The results show that the Ce³⁺ ion occupies the position of the Y³⁺ ion,while the Mn²⁺ occupies the Mg²⁺?Al1?ion site and the Al2 site.By testing the fluorescence spectra,it can be observed that the emission peaks of YMAS:Ce³⁺,Mn²⁺ phosphors correspond to the yellow light emission of Ce³⁺ ions at 568 nm and the red light emission of Mn²⁺?I?at 613 nm and Mn²⁺?II?at 723 nm,respectively.It's wide excitation band is located in the range of 300?500nm,which can be matched with commercial near-ultraviolet chips and blue-light chips.At 450 nm excitation,the fluorescence lifetime of Mn²⁺ was increased to 19.10ms and the energy transfer efficiency is up to 72% through Ce³⁺?Mn²⁺ energy transfer.The packaged warm white LED showed a high color rendering index?Ra = 85.4?and a low correlated color temperature?CCT = 4502K?with a luminous efficiency of 32.76 lm/W.The above results indicate that YMAS:Ce³⁺,Mn²⁺ yellow phosphor has great potential for application on blue-based white LEDs.?2?YMAS:Eu³⁺ red phosphor was prepared by high-temperature solid-state reaction in air atmosphere.The samples were subjected to XRD,fluorescence spectroscopy,fluorescence lifetime,and thermal stability tests.XRD test results show that Eu³⁺ successfully entered the matrix.The spectral test results show that the phosphor can be excited by ultraviolet light?394nm?and blue light?464nm?,respectively,and the strongest emission peak is located at 616 nm.The sample has good thermal stability.This type of phosphor can be used as a red light part in a trichromatic white LED,or it can be added to YMAS:Ce³⁺,Mn²⁺ phosphor to increase the red component of its emission spectrum,thereby improving its performance.?3?YMAS:Eu³⁺ phosphor was prepared by high-temperature solid-state reaction under air atmosphere.The XRD test results show that the synthesized material is exactly what we need.The fluorescence spectrum shows that at 367 nm excitation,the emission band is in the range of 450 nm to 700 nm,and both blue?487nm?and green?592nm?emission are included.Thermal stability tests indicate that the phosphor has good thermal stability.?4?The Dy³⁺ and Eu²⁺ co-doping YMAS phosphors were synthesized by a high-temperature solid-state reaction.By comparing the spectra of YMAS:Eu³⁺ and YMAS:Dy³⁺,it is expected that a single matrix of white light emission can be obtained by co-doping them.XRD testing showed that co-doping did not affect the crystal structure of the matrix.The fluorescence spectrum shows YMAS:Dy³⁺,and the Eu³⁺ spectrum not only shows the emission of Dy³⁺ but also the emission of Eu³⁺.And as the concentration of Eu³⁺ increases,the emission intensity of Dy³⁺ gradually decreases,which confirms the existence of Dy³⁺?Eu³⁺ energy transfer,and the mechanism of energy transfer is studied.The CIE chromaticity diagram shows that with the increase of Eu³⁺ concentration,the color of YMAS:Dy³⁺,Eu³⁺ phosphor gradually changes to the warm white light region,indicating that this type of phosphor has the application potential of single-matrix white LED.