Du Panpan, Li Siyuan, Wang Xuejiao, Zhu Qi, Li Ji-Guang
Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), School of Materials Science and Engineering, Northeastern University, Shenyang, Liaoning 110819, China and Research Center for Functional Materials, National Institute for Materials Science, Namiki 1-1, Tsukuba, Ibaraki 305-0044, Japan.
Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), School of Materials Science and Engineering, Northeastern University, Shenyang, Liaoning 110819, China.
Dalton Trans. 2021 Mar 9;50(9):3337-3347. doi: 10.1039/d0dt04245e.
Solid-state reaction at 1000 °C produces a series of Li-stuffed Li5+2x(La1-yEuy)3(Ta1-xZrx)2O12 garnet phosphors (x = 0-1, y = 0.05-0.6) that exhibit favorable efficiency and thermal stability for red luminescence under either blue or n-UV light excitation, where the optimal composition was identified to be x = 0.5 and y = 0.4. The concentration quenching of luminescence was determined to occur via electric dipole-dipole interactions. Zr4+ substitution for Ta5+, accompanied by additional Li+ for charge compensation, was found via Rietveld structure refinement and Raman/UV-Vis spectroscopy to profoundly affect the tetrahedral and octahedral occupancies of Li, the symmetry of (La/Eu)O8 dodecahedron, and the bandgap of the host lattice and cation disorder, with which the systematically varying excitation and emission behaviors of Eu3+ were deciphered. The Li6(La0.6Eu0.4)3(Ta0.5Zr0.5)2O12 optimal phosphor showed quantum yields of ∼40 and 48% under 393 and 463 nm excitations, respectively, a fluorescence lifetime of ∼0.66 ms for its main emission at 610 nm, color coordinates of around (0.653, 0.347), and can retain as high as ∼85% of its room-temperature emission intensity at 423 K. The phosphor also exhibited a favorable performance for n-UV excited LED lighting.
在1000℃下的固态反应产生了一系列锂填充的Li5+2x(La1-yEuy)3(Ta1-xZrx)2O12石榴石荧光粉（x = 0 - 1，y = 0.05 - 0.6），在蓝光或近紫外光激发下，这些荧光粉对红色发光表现出良好的效率和热稳定性，其中最佳组成确定为x = 0.5和y = 0.4。通过电偶极-偶极相互作用确定了发光的浓度猝灭。通过Rietveld结构精修以及拉曼光谱/紫外-可见光谱发现，用Zr4+取代Ta5+并伴随额外的Li+进行电荷补偿，会深刻影响Li的四面体和八面体占有率、(La/Eu)O8十二面体的对称性、主体晶格的带隙以及阳离子无序度，据此解读了Eu3+系统变化的激发和发射行为。最佳荧光粉Li6(La0.6Eu0.4)3(Ta0.5Zr0.5)2O12在393和463 nm激发下的量子产率分别约为40%和48%，其在610 nm处的主要发射的荧光寿命约为0.66 ms，色坐标约为(0.653, 0.347)，并且在423 K时可保留高达约85%的室温发射强度。该荧光粉在近紫外激发的发光二极管照明方面也表现出良好的性能。
