Design, Luminescence Mechanism And Application Of β-Ca₃ (PO₄)₂ Luminescent Materials For Full-spectrum LEDs

Compounds based on theβ-Ca₃（PO₄）₂-type can provide different crystal environment and cationic sites for rare earth ions and transition metal ions,and have attracted widespread attention as a luminescent material matrix in recent years.In view of the low color rendering index of white light LEDs and the urgent need for luminescent materials for full-spectrum lighting,the compounds withβ-Ca₃（PO₄）₂structure are used as the luminescent material matrix.By using the energy transfer model,co-doping strategy of activators,and chemical synthesis strategy,a series of Eu^2+/3+and/or Mn²⁺ion activated luminescent materials were prepared by high temperature solid state reaction and sol gel method,realizing full-spectrum emission in a single phase luminescent material.The structure-related luminescence mechanism of the prepared luminescent material and the practical application value in the field of white light LEDs were deeply studied.The thesis mainly includes the following two research parts:（1）Realizing an impressive red-emitting Ca₉Mn Na（PO₄）₇ phosphor through a dual function based on disturbing structural confinement and energy transfer.The chemical co-substitution strategy was used to optimize the luminescence properties of the Ca₉Mn Na（PO₄）₇ phosphor and achieve excellent red luminescence.The efficient Eu-Mn energy transfer process makes the quantum yield of Ca₉Mn_0.95Na（PO₄）₇:0.05Eu²⁺sample as high as 82%,and the LEDs prepared with Ca₉Mn_0.95Na（PO₄）₇:0.05Eu²⁺as red emission material has a high color rendering index（Ra=80.5）and a low relative color temperature（4956 K）.The results show that the prepared red luminescent materials can be used as an important component of LED with excellent luminescent propertiesFurthermore,the luminescence properties of Ca₉Mn Na（PO₄）₇:Eu²⁺were regulated through chemical synthesis strategy.Ca₉Mn Na（PO₄）₇@Ca₉Eu Na（PO₄）₇ solid solution materials with highly dispersed luminescence centers were prepared by the efficient two-step sol-gel method for the first time.The photoluminescence spectra of Eu²⁺in the lattice of Ca₉Mn Na（PO₄）₇ were regulated,and the white light emission was obtained from the single phase phosphors.This work proves that the sol-gel method is an effective way to adjust the luminescence performance,and also provides another method to adjust the photoluminescence spectra of luminescent materials besides ion substitution strategy.（2）The effect of local structure on the luminescence of Eu^2+/3+in ternary phosphate solid solutions by cationic heterovalent substitution and their application in white LEDs.Based on the heterovalent substitution strategy of Y³⁺and Na⁺to Ca²⁺,a series of Eu^2+/3+doped Ca₉Na_3xY_1-x（PO₄）₇（0≤x≤1/2）and Ca_9+yNa_3/2-y/2Y_（1-y）/2（PO₄）₇（0≤y≤1）phosphors were designed.Changing the substitution ratio of Y³⁺and Na⁺to Ca²⁺can adjust the occupation of Eu^2+/3+at different positions,finally achieving the tuning of phosphor luminescence.Through the co-doping of Eu²⁺and Mn²⁺,the full emission spectrum cover in visible light region（400-800 nm）was realized.White LEDs prepared with the luminescent material have high color rendering index（>80）and tunable color temperature in the range of 2854～7000 K.This work provides an effective strategy for designing novel luminescent materials and realizing multi-site adjustment of activator ions.