Preparation And Luminescence Properties Of The Double Perovskite LiLaMgWO₆ Red Phosphor For WLED

White Light Emitting Diode（WLED）has the advantages of high efficiency,long life,low power consumption,compact structure,stability and reliability,and environmental protection.As the fourth-generation artificial lighting source,WLED starts a new era in the lighting industry.Currently,the commercial WLED design scheme is to composite the blue LED chip and the yellow phosphor,but its color temperature and color rendering index are not ideal.There are two mainstream design schemes for the new WLED to solve the problem of color temperature and color rendering index.The first scheme is to use the blue light emitted by the blue LED chip to make the red and green phosphors excited to produce red and green light.The three colors light is combined into white light.The second solution is to use ultraviolet or near-ultraviolet LED chips as the excitation light source,and rely on the excited light of the red,green and blue phosphors to obtain white light.Both of these two design schemes put forward higher requirements on the luminous properties of the red phosphor.In this thesis,LiLaMgWO₆:Eu³⁺and LiLaMgWO₆:Bi red phosphors have been prepared by high-temperature solid-phase method and ion doping,without changing the double perovskite structure of LiLaMgWO₆.The luminescence properties of these red phosphors have been studied as follows:（1）According to the transition selection law,the 617 nm main peak of the photoluminescence emission spectrum of LiLaMgWO₆:Eu³⁺red phosphor excited by 396 nm is caused by the ⁵D₀→⁷F₂electric dipole transition of Eu³⁺.The optimal doping concentration of the phosphor luminescence is about 30%,the luminous intensity integral at its main peak accounts for about 72%of the total luminescence.The red luminescence is concentrated,which is suitable for the WLED.Plant photosynthesis has a significant effect on the absorption of 610～720 nm light waves.The integrated luminous intensity of the phosphor,at 610～720 nm light waves,accounts for about 87%of the total luminescence,which is suitable for the plant light.（2）The diffuse reflectance spectrum of LiLaMgWO₆:Bi red phosphor confirms that the doping of Bi element will cause the band gap to become smaller,which is beneficial to the excited light of the phosphor.Under the excitation of 355 nm,the emission peaks of 553 nm and 697 nm of this phosphor correspond to the ³P₁→¹S₀ transition of Bi³⁺and the ²P_3/2→²P_1/2 transition of Bi²⁺,respectively.The optimal doping concentration for the luminescence of the red phosphor is about 7‰.The luminous intensity,integral of the red light,accounts for about 89%of the total luminescence.The luminous intensity of Li La_0.993Mg WO₆:0.007Bi red phosphor,excited at 355 nm,in the temperature range of 300～510 K showed a trend of first increasing and then decreasing,with the strongest luminescence at 360 K.The luminescence of the LiLaMgWO₆:Bi red phosphor,which has the reduced ion valence,is more concentrated than that of the LiLaMgWO₆:Bi red phosphor.This confirms that the red phosphor is suitable for WLED.