绿色荧光粉LaGaO3∶Tb3+,Sn4+的制备及发光性能研究

doi:10.3964/j.issn.1000-0593(2020)01-0065-06

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摘要：稀土掺杂LaGaO₃荧光粉因具有优良的发光性能、高的显色性和稳定性等优点而适合应用于场发射显示和LED器件中，其中，LaGaO₃∶Tb³⁺发光强度和色纯度高于商用Y₂SiO₅∶Ce³⁺荧光粉。通过共掺Sn⁴⁺提高LaGaO₃∶Tb³⁺荧光粉的发光性能使其更好地应用在白光LED中；利用高温固相法制备一系列LaGaO₃∶Tb³⁺和LaGaO₃∶Tb³⁺,Sn⁴⁺绿色荧光粉，并通过XRD和光致发光光谱分别对样品的晶体结构和发光性能进行表征。结果表明：掺杂Tb³⁺和Sn⁴⁺分别取代La³⁺和Ga³⁺进入到基质LaGaO₃的晶体结构中，并未出现其他杂相，形成纯相的荧光粉。样品的激发光谱均由位于231，257和274 nm处的宽峰和位于300～500 nm锐利峰组成，其中，231和274 nm分别对应于Tb³⁺的4f-5d自旋允许跃迁（LS，⁷F₆→⁷D_J，ΔS=0）和自旋禁戒跃迁（⁷F₆→⁹D_J，ΔS=1）；257 nm归因于基质中GaO₆基团自激活光学中心的跃迁；300～500 nm锐利峰归因于Tb³⁺的f-f特征激发跃迁，如⁷F₆→⁵H₆，⁵H₇，⁵L₆，⁵L₉，⁵L₁₀, ⁵G₉和⁵D₄。相对于LaGaO₃∶Tb³⁺，共掺Sn⁴⁺主要提高Tb³⁺的4f-4f特征激发跃迁强度，主激发峰由Tb³⁺的f-d跃迁变为f-f跃迁。在380 nm光激发下，样品LaGaO₃∶Tb³⁺和LaGaO₃∶Tb³⁺,Sn⁴⁺的发射光谱均由Tb³⁺的特征跃迁⁵D₄→⁷F₆ (487和493 nm), ⁵D₄→⁷F₅ (545 nm), ⁵D₄→⁷F₄(584和589 nm)和⁵D₄→⁷F₃ (622 nm)组成，其中，以⁵D₄→⁷F₅跃迁为主。样品LaGaO₃∶Tb³⁺和LaGaO₃∶Tb³⁺,Sn⁴⁺的CIE色坐标分别位于绿色区域（0.287 4, 0.545 9）和（0.279 7, 0.576 1）；荧光寿命分别为1.63和1.38 ms；色纯度分别为54.81%和62.67%。共掺Sn⁴⁺不仅没有影响发射峰的位置，而且提高了发射强度（提高近一倍），改变样品的浓度猝灭机理，由双极子-双极子(d-d)相互作用转变为双极子-四极子(d-q)相互作用。LaGaO₃∶Tb³⁺和LaGaO₃∶Tb³⁺,Sn⁴⁺中Tb³⁺的最佳掺杂量分别为0.05和0.07；Sn⁴⁺的最佳掺杂量为0.03，说明Sn⁴⁺共掺提高Tb³⁺的最佳掺杂量，有利于发光强度的提高。样品LaGaO₃∶0.05Tb³⁺和LaGaO₃∶0.07Tb³⁺,0.03Sn⁴⁺的光视效能（LER）分别为464和485 lm·W^-1；内量子效率分别为21.8%和39.2%。随着温度的升高，由于热猝灭，样品LaGaO₃∶Tb³⁺,Sn⁴⁺的发光强度逐渐下降；但在140 ℃时，发光强度仍可保持70%以上；通过Arrhenian公式计算，热活化能ΔE为0.169 0 eV，说明样品具有良好的稳定性。结果表明：LaGaO₃∶Tb³⁺,Sn⁴⁺可作为绿色荧光粉实际应用于UV激发的白光LED器件中。

关键词：绿色荧光粉；光致发光；LaGaO₃∶Tb³⁺,Sn⁴⁺

Abstract：Rare earth doped LaGaO₃ phosphors could be suitable for use in field emission display and LED applications, owing to the excellent luminescent properties, high color rendition and stability, et al. The luminescent intensity and color purity of LaGaO₃∶Tb³⁺ are higher than those of commercial Y₂SiO₅∶Ce³⁺ phosphor. In order to expand application in white LED, the luminescent intensity of LaGaO₃∶Tb³⁺ is enhanced by co-doping Sn⁴⁺ ions in this paper. A series of green phosphor LaGaO₃∶Tb³⁺ and LaGaO₃∶Tb³⁺,Sn⁴⁺ were synthesized by high-temperature solid-state method. The crystal structures and luminescent properties were characterized by XRD and photoluminescence spectrum, respectively. The results show that all Tb³⁺ and Sn⁴⁺ ions preferably substitute for La³⁺ and Ga³⁺ ions, respectively, in the crystal lattice of LaGaO₃ without impurity phases, indicating obtained samples are single phase phosphors. All excitation spectra consist of some broad peaks (231, 257, and 274 nm) and sharp peaks (from 300 to 500 nm). The bands at 231 and 274 nm are assigned to the spin allowed transition (LS, ⁷F₆→⁷D_J, ΔS=0) and the spin forbidden transition (⁷F₆→⁹D_J, ΔS=1) for 4f-5d of Tb³⁺, respectively. The band at 257 nm is assigned to the transition of a self-activated optical center related to octahedral coordinated GaO₆ groups. Some excitation peaks in the range of 300～500 nm are attributed to f-f characteristic transitions of Tb³⁺, such as ⁷F₆→⁵H₆, ⁵H₇, ⁵L₆, ⁵L₉, ⁵L₁₀, ⁵G₉ and ⁵D₄. Compared with LaGaO₃∶Tb³⁺, co-doped Sn⁴⁺ion can enhance the 4f-4f characteristic excitation intensity of Tb³⁺. The main excitation peak changes from f-d transition of Tb³⁺ to its f-f transition. Under excitation at 308 nm, the emission spectra of LaGaO₃∶Tb³⁺ and LaGaO₃∶Tb³⁺,Sn⁴ all consist of Tb³⁺ ions characteristic transitions, such as ⁵D₄→⁷F₆ (487, 493 nm), ⁵D₄→⁷F₅ (545 nm), ⁵D₄→⁷F₄ (584, 589 nm), and ⁵D₄→⁷F₃ (622 nm). The strongest emission peak is at 545 nm. The CIE color coordinates of LaGaO₃∶Tb³⁺ and LaGaO₃∶Tb³⁺,Sn⁴⁺ are (0.287 4, 0.545 9) and (0.279 7, 0.576 1) in green region, respectively. The fluorescence lifetime of LaGaO₃∶Tb³⁺ and LaGaO₃∶Tb³⁺,Sn⁴⁺are 1.63 and 1.38 ms, respectively；the color purity values of LaGaO₃∶Tb³⁺ and LaGaO₃∶Tb³⁺,Sn⁴⁺ are 54.81% and 62.67%, respectively. Co-doped Sn⁴⁺ ion has no impact on the position of emission peaks, but the emission intensity of Tb³⁺ increases to nearly double. Mechanism of concentration quenching can be changed from dipole-quadrupole (d-q) to quadrupole-quadrupole (q-q) interactions. The optimum doping concentration of Tb³⁺ is 0.05 and 0.07 in the LaGaO₃∶Tb³⁺and LaGaO₃∶Tb³⁺,Sn⁴⁺, respectively. The optimum Sn⁴⁺ doping concentration is 0.03. The optimum doping concentration of Tb³⁺ increases by co-doped Sn⁴⁺, which is beneficial to improving luminous intensity. The luminous efficacy values of the radiation (LER) of LaGaO₃∶0.05Tb³⁺ and LaGaO₃∶0.07Tb³⁺, 0.03Sn⁴⁺ are 464 and 485 lm·W^-1, respectively. The internal quantum efficiency values of LaGaO₃∶0.05Tb³⁺ and LaGaO₃∶0.07Tb³⁺, 0∶03Sn⁴⁺ are 21.8% and 39.2%, respectively. The emission intensity decreases gradually with the increasing temperature due to the thermal quenching. The emission intensity of the LaGaO₃∶Tb³⁺,Sn⁴⁺ sample remains to be above 70% at 150 ℃. According to the Arrhenius equation, the thermal activation energy ΔE for quenching is calculated to be 0.169 0 eV, which indicates that this phosphor has excellent thermal stability. All the results show that the LaGaO₃∶Tb³⁺,Sn⁴⁺ phosphor is a promising green phosphor for the n-UV excited w-LEDs.

Key words：Green phosphors; Luminescence; LaGaO₃∶Tb³⁺,Sn⁴⁺

收稿日期: 2018-11-16 修订日期: 2019-03-20

中图分类号:

O482.31

基金资助: 国家自然科学基金项目(51474133)资助

通讯作者: 赵文玉 E-mail: zhaowenyu2011@hotmail.com

作者简介: 樊彬，1982年生，内蒙古科技大学化学与化工学院讲师 e-mail: fb8726@163.com

引用本文:

樊彬，刘军，戚世梅，赵文玉. 绿色荧光粉LaGaO₃∶Tb³⁺,Sn⁴⁺的制备及发光性能研究[J]. 光谱学与光谱分析, 2020, 40(01): 65-70.
FAN Bin, LIU Jun, QI Shi-mei, ZHAO Wen-yu. Preparation and Luminescent Properties of Green Phosphors LaGaO₃∶Tb³⁺,Sn⁴⁺. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2020, 40(01): 65-70.

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https://www.gpxygpfx.com/CN/10.3964/j.issn.1000-0593(2020)01-0065-06 或 https://www.gpxygpfx.com/CN/Y2020/V40/I01/65