白光LED用Li^+/La^3+共掺杂BaSi2O5∶Eu^2+绿光发射荧光粉的制备及其发光性能和热稳定性

Preparation,Luminescence and Thermal Stability of Li^+/La^3+Co-doped Single-phased BaSi2O5∶Eu^2+Green Emitting Phosphors for White LEDs

通过Li^+/La^3+同比例共掺杂策略,在氢气气氛下烧结制备了Li0.06La0.06Ba0.84Si2O5∶4%Eu^2+(LLBSO∶Eu2+)高效绿色发光荧光粉。相比于未掺杂样品Ba0.96Si2O5∶4%Eu2+(BSO∶Eu^2+),Li^+/La^3+共掺有助于单一相LLBSO∶Eu^2+荧光粉的合成,能有效降低烧结的温度和缩短合成时间。我们发现该策略节约荧光粉合成成本的同时,也可以显著提高其光学性能。相关测试表明,Li+/La3+共掺杂样品平均颗粒尺寸主要分布在1.1~2.7μm,颗粒团聚现象不明显,符合涂覆LED芯片要求。该样品可以有效地被365 nm近紫外LED芯片激发,产生位于502 nm的强的宽带绿光发射,其归属于Eu2+的5d-4f跃迁,发光强度是未掺杂样品的168%。此外,LLBSO∶Eu^2+荧光粉在150℃时发光强度仍保持在室温时的98%左右,具有良好的热稳定性。该样品CIE坐标位于绿光区(0.217,0.410)。通过绿粉/红粉和绿粉/红粉/蓝粉混粉策略,制得了色温为2918~4037 K的白色发光LED,其显色指数(Ra)均大于85,具有良好的热稳定性。实验结果表明,Li^+/La^3+共掺单一相的BSO∶Eu^2+绿色发光荧光粉是制备近紫外激发白光发射LED的优良候选荧光粉材料。

Li^+/La^3+co-doped Li0.06La0.06Ba0.84Si2O5∶4%Eu^2+(LLBSO∶Eu^2+)green-emitting phosphors were prepared through a high-temperature solid state reaction.Compared with undoped Ba0.96Si2O5∶4%Eu2+(BSO∶Eu^2+)sample,it can be found that Li+/La3+co-doping is an efficient strategy for synthesizing single-phased LLBSO∶Eu^2+at lower temperature in less synthesis time.Our results indicate that this strategy can lead to not only the reduced cost but also the improved optical performances.The related tests suggest that,for Li+/La3+co-doped BSO∶Eu^2+phosphors,the particle size is in the range of 1.1-2.7μm and no obvious aggregation can be found,suggesting that it meets the requirements for coating LED chips.Upon near-ultraviolet LED chip(365 nm)excitation,LLBSO∶Eu2+exhibits a strong broadband emission around 502 nm,which is attributed to the 5d-4f transition of Eu2+.Its luminescent intensity reaches 168%as strong as that of the undoped sample.Furthermore,for LLBSO∶Eu^2+phosphor,the luminescent intensity measured at 150℃is^98%as strong as that measured at room temperature,suggesting it has good thermal stability.The CIE coordinate of LLBSO∶Eu^2+phosphors is(0.217,0.410),which locates in the green light region.White LEDs with different color temperatures ranging from 2918 K to 4037 K,were fabricated using blend strategies.These LEDs exhibit high color rendering index(Ra>85)and good thermal stability.Our studies suggest that LLBSO∶Eu^2+green-emitting phosphor is one kind of candidates for fabricating near-ultraviolet excited white LEDs.