高光效高热稳定性蓝色荧光粉Ca2-ySrySiO4∶Ce3+,Li+的组成筛选和发光机理

Composition-Screening and Luminescent Mechanism in CaSrSiO∶Ce,Li for High Quantum Efficiency and Thermally Stable Blue-Emitting Phosphor

采用高温固相法合成了一系列Ca2-x-ySry-xSiO4∶x Ce^3+,x Li^+蓝色固溶体荧光粉。XRD结果表明,所合成的固溶体荧光粉均为单一物相。随着Sr2+成分的增加,Ca2-ySry SiO4物相从单斜晶系β-Ca2SiO4向正交晶系α′-Ca2SiO4转变,发射光谱逐渐红移。组成为Ca1.75Sr0.25SiO4时,荧光粉的发射波长最长(454 nm),Stokes位移最大。基质为Ca1.1Sr0.9SiO4的晶体结构可诱导掺杂离子Ce^3+取代SrO10格位、Li^+取代CaO8格位。优化的荧光粉Ca1.05Sr0.85SiO4∶0.05Ce^3+,0.05Li^+(CS0.85SO∶CeLi)在375 nm紫外光激发下,发射445 nm的蓝光,内量子效率(IQE)达到91.18%,200℃时发射强度保持室温发光强度的98.70%。根据晶体结构、晶体场分裂和掺杂离子质心位移等理论,讨论了CS0.85SO∶CeLi综合发光效应最佳的内在原因。

Ca2-x-ySry-xSiO4∶x Ce^3+,x Li^+solid solution phosphors were designed and prepared by a high temperature solid-state reaction in a reductive atmosphere.The results of the XRD reveal that as-synthesized samples are single-phase compounds,and a phase transition from monoclinicβ-Ca2SiO4 to orthogonalα′-Ca2SiO4 exists(y=0~0.25).The excitation and emission spectra of the phosphors showed a gradual redshift with the increase of Sr content(y)from 0 to 0.25,which showed the largest Stokes shift(73 nm)for Ca1.75Sr0.25SiO4,and subsequently a blueshift showed up after a further increase of y value.Moreover,the host of Ca1.1Sr0.9SiO4 can induce Ce^3+ions preferentially to occupy the ten-coordinated Sr2+sites(SrO10)while Li^+ions replace the eight-coordinated Ca2+sites(CaO8).The optimized phosphor Ca1.05Sr0.85SiO4∶0.05 Ce^3+,0.05 Li^+(CS0.85SO∶Ce)possessed a high internal quantum efficiency(IQE)reached 91.18%.The temperature-dependent photoluminescence(PL)spectra showed that the PL intensity of CS0.85SO∶Ce at 200℃maintained 98.70%of that at room temperature.The luminescent mechanisms were discussed in detailed according to crystal structure,crystal field theory and the Dorenbos model.