Research Of Regulative Luminescence Properties Of MX₄B₃O_?9-3y/2?N_y:Eu²⁺?M=Li,Na,K;X=Mg,Ca,Sr,Ba? Phosphors

In this thesis, a series of orthoborate phosphors MX4B3O_?9-3y/2?Ny:Eu²⁺ ?M=Li, Na, K; X=Mg, Ca, Sr, Ba;? with single matrix and activation agent ion have been synthesized successfully through a high-temperature solid-phase method. By replacing the alkali metal ions ?Li+, Na+, K+?, the alkaline earth metals ions (Mg2+, Ca²⁺, Sr2+, Ba2+), or the anions ?N3"?, and combined with changes of the structure and spectrum, the regulative luminescence properties of these phosphors have been studied.For the substitution of alkali metal ions, the replacing between Li+and Na+ in the LiSr₄?BO₃?₃:Eu²⁺phosphors was found not to change their fundamental structure and luminescence properties. Since KSr₄?BO₃?₃ and LiSr₄?BO₃?₃ have different structures, the K+doping can change the structure of the LiSr₄?BO₃?₃:Eu²⁺phosphors and introduce impurity phase, so the substitution of K+will not be account in the next study.For the substitution of alkaline earth metals ions, with the increase of Ca²⁺ ions in the LiSr_4-xCax?BO₃?₃ host, the lattice constants and unit cell volume increased gradually, while the crystal structure remained a same cubic unit cell. Based on the analytical data of the crystal structure, the band structure, the blue shift of emission spectra has been ascribed to the nephelauxetic effect. The emission colors point of the obtained phosphors can be continuously tuned from orange-red ?05524,0.4270? to yellow-green ?0.1895,0.4718?. The packaged white LED combined with phosphor and LED chip have a color-rendering index of 85.3 around the correlated color temperature of 5083 K. With the increase of Ba2+ions in the NaSr₄-xBax?BO₃?₃:Eu²⁺ host, the lattice constants and unit cell volume decreased gradually, while the crystal structure remained a same cubic unit cell. According the analytical data of the crystal structure, the band structure, the blue shift of emission spectra should be ascribed to the crystal filed splitting effect. The emission colors piont of the obtained phosphors can be continuously tuned from orange-red ?0.4795,0.4070? to yellow-green ?0.3432, 0.4665?. The packaged white LED combined with phosphor and LED chip have a color-rendering index of 88.5 around the correlated color temperature of 6800 K. Since the ionic radius of Mg2+ion and Sr2+ ion have obvious difference, so the substitution of Mg2+ ions will introduce impurity phase.In the study of substitution of anions, we found that the mutual replacement between N and O barely led to an obvious change on the crystal structure of Na/LiSr_4-yB3O?9-3x/2?Nx:yEu²⁺ phosphors, and but the introduction of N could effectively enhance their PL intensity. According the analysis of crystal structure, with the increase of the substitution of N content, Na/LiSr_4-yB3O?9-3x/2?Nx:yEu²⁺showed no obvious structure change and always remained a cubic structure which belong to the Ia-3d space group. The analysis of PL spectra demonstrated that N3-successfully entered into the phosphor matrixes. The N doping could introduce some impurity energy levels which were close to the bottom of the conduction bands, which caused the narrower band gap of matrixes host. Therefore, the absorption in the visible spectral range was enhanced, which improved the PL intensity of Na/LiSr_4-yB3O?9-3x/2?Nx:yEu²⁺ phosphors.