高分子网络凝胶法低温合成YAG：Tb3+荧光粉

以金属硝酸盐为原料,丙烯酰胺为聚合单体以及N,N-亚甲基双丙烯桥酰胺为胶联剂,采用高分子网络凝胶法在低温下合成精细粒度Y₃Al₅O₁₂:Tb³⁺(YAG:Tb³⁺)荧光粉。分别用热重-差热分析(TG-DTA)、X射线衍射(XRD)、扫描电子显微镜(SEM),以及激发和发射光谱测量对样品进行了表征,考察了烧结温度对样品结晶程度、颗粒大小的影响,以及样品发光性能与烧结温度和Tb³⁺浓度的关系。结果表明:YAG晶相形成温度为850℃;粉体颗粒大小均匀,随着烧结温度的升高,颗粒粒径增大,结晶程度提高;观察到Tb³⁺中4f-5d的吸收带以及⁵D₄-⁷F_j(j=6,5,4,3)的特征发射带,最强吸收与最强发射分别发生在272,541.8 nm,与量子理论(E=1.24/λ)的计算结果相吻合,其发光强度随烧结温度的升高而增强;观察到了Tb³⁺在Y₃Al₅O₁₂中的浓度猝灭现象。

Synthesis of YAG:Tb~(3 ) Phosphors by Polymer Gel Method at Low Temperature

Using acrylamide (CH₂=CHCONH₂) to form long chains of polyacrylamide and a cross-linker N′,N′-methylenebisacrylamide (CH₂=CHCONHCH₂NHCOCH=CH₂) to achieve tangled network,hydro-gen peroxide (H₂O₂) as initiator and N,N,N′,N′-tetramethylethylenediamide [(CH₃)₂NCH₂CH₂N(CH₃)₂] as activator,we have successfully prepared the precursor from nitrates (aluminum nitrate,yttrium nitrate,and terbium nitrate),the precursor was subsequently heat-treated from 700℃ to 1 400℃ for 4 h to form terbium-doped yttrium aluminum garnet (YAG:Tb³⁺) phosphor powders.The synthesized powders were characterized by thermogravimertry-differential thermal analysis (TG-DTA),X-ray diffraction (XRD),scanning electron microscopy (SEM) and fluorescence spectrometer.XRD analysis demonstrated that phase-pure YAG was ob-tained directly from the precursor at 850℃,without the formation of any intermediate phase (s) of YAP (YAlO₃) and/or YAM (YAl₄O₉).SEM images showed the particles were uniform,and the grain size in-creased with a rise in heat-treating temperature.The excitation spectrum consisted of three peaks with the highest intensity at 272 nm,the second at 230 nm and the third at 324 nm,respectively,all corresponding to the Th³⁺ 4f-5d absorption.⁵D₄-⁷F_j(j=6,5,4,3) emissions were also observed clearly,the highest emission peaked is at 541.8 nm for the ⁵D₄-⁷F₅ transition of Th³⁺,the second is for the ⁵D₄-⁷F₆ with two lines at 486 nm and 490 nm,and the weaker emission from about 570 nm to 630 nm was corresponding to the transi-tions of ⁵D₄-⁷F₄ and ⁵D₄-⁷F₃.Enhanced luminescence intensity could be obtained by rising the sintering tem-perature which may improve the crystallization of YAG particles and favor the doping of Tb³⁺ ions into YAG lattices.Concentration quenching phenomenon appeared when Tb³⁺ molefraction (value of x) in (Y_1-xTb_x)₃Al₅O₁₂ is over 0.06.