Preparation And Luminescence Properties Research Of Fluorescent Conversion Materials For W-LEDs

Nowadays,the commonly used method for white LEDs is coating a mixture of YAG:Ce³⁺phosphor and organic resin on the surface of blue LED chips.However,its low color rendering index,high color temperature and poor thermal stability and other shortcomings seriously limit its application in high-quality and high-power devices.In this paper,three types of fluorescent conversion materials,Mn⁴⁺doped oxide red phosphor,Dy³⁺/Tm³⁺co-doped phosphor fluorescent glass and YAG:Ce³⁺fluorescent glass ceramics,were designed and synthesized for the special requirements of high quality high-power LED devices on the color stability and luminescence efficiency of fluorescent conversion materials,and their properties were studied.（1）Firstly,CaO-0.5Al₂O₃-0.5Nb₂O₅:Mn⁴⁺red phosphor was prepared through high temperature solid reaction.The red-light center was located at 657 nm under the 331 nm excitation,this is the one of the most closed to 650 nm red phosphor emission wavelength.The color index R_a by 70 promoted to 78 before using the red phosphor;（2）Then Dy³⁺/Tm³⁺single-doped and co-doped phosphate fluorescent glass was prepared by the traditional melting quenching method.The color coordinate was（0.3300,0.3439）and the relevant color temperature was 5533 K.The luminescence intensity of the sample can maintain at least 85%when the temperature was elevated to 200°C of its strength at room temperature,showing good thermal stability;（3）YAG:Ce³⁺composite Mn²⁺ion-doped phosphate fluorescent glass ceramics（PIG）was finally prepared by low-temperature co-sintering.Based on the prepared PIG encapsulated white LED color coordinate was（0.3252,0.3270）,the luminous efficiency could reach 169.89lm/W,the color temperature was 5853 K,and the color index was 74.4.The results show that the fluorescent glass ceramic has potential value in the application of high-power LED;...