Research On Preparation And Luminescent Properties Of Ba₂Ln（BO₃）₂Cl、CaWO₄ Phosphor

In this article, Ba2Ln(BO3)2Cl (Ln=Y3+, Gd3+):Sm3+,Eu3+red phosphors and alkali metal ions doping CaWO4:Tb3+as charge compensation were synthesized successfully via high temperature solid state method. The XRD, photoluminescence, fluorescence lifetime, afterglow decay and thermoluminescence(TL) are employed to investigate, and the results as follows:1. Luminescence properties and energy transfer in the red emitting phosphors Ba2Ln(BO3)2Cl:Sm3+, Eu3+(Ln=Y, Gd)According to the research on XRD of Sm3+/Eu3+single-doped and co-doped Ba2Ln(BO3)2Cl (Ln=Y,Gd) phosphors, the crystal structure studies present that samples Ba2Ln(BO3)2Cl belong to the successful isomorphic substitution for Ln3+sites in the Ba2Yb(BO3)2Cl host, which crystallized in a monoclinic unit cell with space group P21/m. And it can be found that the emission intensity of Sm3+at 603nm decreases and that of Eu3+ at 593nm increases with increasing Eu3+doping concentration, which provides indirect evidence of the Sm3+/Eu3+energy transfer. The decreasing decay lifetime of Sm3+with the growth concentration of Eu3+confirms the occurrence of energy transfer from Sm3+to Eu3+. Further investigation on concentration-dependent emission spectra shows that the concentration quenching mechanism was verified to be the electric dipole-quadrupole interaction.After systemically investigating, all the results indicate that the addition of Sm3+could increase absorption in the n-UV region (-400 nm), which makes the obtained phosphors match well with LED (InGaN based) emission. Hence, they are attractive for application in white LEDs.2. Charge compensation for the luminescence of CaWO4:Tb3+phosphorThe results suggested that a series of CaWO4:Tb3+, M+(M=Li, Na, K) novel luminescent materials differences on the optical properties and afterglow properties. Na+ ions with the minimum radius are more likely to enter the lattice, which compensation effect is most obvious for the charge imbalance of Tb3+ion doping and volume compensation of the substrate. Na+ions can improve the luminous efficiency and energy transfer efficiency, so as to improve the luminescence of Tb3+ions. For the afterglow properties of the sample, the afterglow of the sample from Tb3+of 5D4→7 F5,6 charge transitions. Charge compensation for the afterglow emission and themoluminescence shapes without any impacts, just intensity change, this may be due to charge compensation when the deference radius of alkali metal ion which affect different affects on trap. Different radius of the alkali metal ion doping makes the material itself defects caused by trap concentration have some degree of increase or decrease, thus different degrees of influence on the afterglow properties. Compared with other alkali metal ions influence on the lattice distortion, Li+enterring the lattice caused the biggest change of trap concentration. So that, the compensation effect of Li+is most obvious on the material of the afterglow performance.