掺Gd3+的LiYF4∶Yb3+/Ho3+微米晶体制备以及在防伪中的应用研究

doi:10.3964/j.issn.1000-0593(2022)11-3581-07

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摘要：研究一种具有良好上转换发光性能的稀土掺杂发光材料，对于防伪技术领域具有非常重要的意义。为了改善LiYF₄∶Yb³⁺/Ho³⁺微米晶体的上转换发光性能，采用水热合成法成功制备了一系列Gd³⁺掺杂的LiYF₄∶Yb³⁺/Ho³⁺微米晶体，并采用X射线衍射(XRD)和扫描电子显微镜(SEM)对样品的相纯度和晶体形貌尺寸进行表征；在980 nm激光激发下，通过荧光光谱测试对LiGd_xY_1-xF₄∶Yb³⁺/Ho³⁺微米晶体的上转换发光性能进行分析。首先，研究了LiGd_xY_1-xF₄∶Yb³⁺/Ho³⁺微米晶体的晶体结构、尺寸、形貌和上转换发光性能的影响。结果显示，LiGd_xY_1-xF₄∶Yb³⁺/Ho³⁺微米晶体样品的XRD衍射峰与四方相的LiYF₄标准卡（PDF#17-0874）特征峰的位置完全对应且没有其他杂峰，SEM实验结果显示晶体形貌为八面体形状，表明成功合成了纯四方相的LiGd_xY_1-xF₄∶Yb³⁺/Ho³⁺微米晶体；荧光光谱测试结果显示，样品的上转换发光强度随着Gd³⁺掺杂比例的升高呈现出先增强后减弱的趋势，并且在Gd³⁺掺杂浓度为30 mol%时达到最强。其次，进一步研究了Gd³⁺掺杂浓度30 mol%样品的上转换发光性能与激发功率之间的关系，激发功率为0.5~1.5 W。LiGd_0.3Y_0.49F₄∶Yb³⁺/Ho³⁺微米晶体的红色和绿色上转换发光强度之比(R/G)随着激发功率的增加只发生大约12%的变化，样品的上转换发光并没有因为激发功率的增加而发生明显的变色，仍然可以发出稳定明亮的绿色光。这一现象表明，Gd³⁺的掺入很好地改善了样品的上转换发光性能，这种稳定高效的发光性能保证了其良好的防伪性能。最后，将Gd³⁺掺杂浓度为30 mol%的LiYF₄∶Yb³⁺/Ho³⁺微米晶体粉末与丝网金属油墨按照一定比例混合制成丝网防伪油墨，通过丝网印刷技术在玻璃基底上印制了“西安”字样的防伪标识图案，经过干燥处理后在980 nm激光的激发下，发出明亮且稳定的绿色可见光，制成的防伪标识图案具有发光强度高、易于识别、不易脱落的特点，可被广泛应用于防伪领域。

关键词：上转换发光；Li(Gd_xY_1-x)_0.79F₄∶Yb_0.2/Ho_0.01；微米晶体；水热合成法；防伪识别；丝网印刷

Abstract：The purpose of this paper is to study a rare earth doped luminescent material with good up-conversion luminescence performance, which is of great significance in anti-counterfeiting technology. In order to improve the up-conversion luminescence performance of LiYF₄∶Yb³⁺/Ho³⁺ micron crystals, a series of Gd³⁺-doped LiYF₄∶Yb³⁺/Ho³⁺ micron crystals were successfully prepared by hydrothermal synthesis method. XRD and Scanning electron microscope (SEM) were used to characterize the samples’ phase purity and crystal morphology. Fluorescence spectra analyzed the upconversion luminescence properties of LiGd_xY_1-xF₄∶Yb³⁺/Ho³⁺ micron crystals under 980nm laser excitation. Firstly, the crystal structure, size, morphology and upconversion luminescence properties of LiGd_xY_1-xF₄∶Yb³⁺/Ho³⁺ micron crystals were investigated. The results show that the XRD diffraction peaks of LiGd_xY_1-xF₄∶Yb³⁺/Ho³⁺ micron crystal samples are exactly corresponding to the characteristic peaks of the tetragonal LiYF₄ standard card (PDF#17-0874) without other peaks. The SEM characterization results show that the crystal morphology is octahedral. It shows that LiGd_xY_1-xF₄∶Yb³⁺/Ho³⁺ micron crystal with pure tetragonal phase was successfully synthesized. Fluorescence spectrum test results showed that the up-conversion luminescence intensity of the samples increased first and then decreased with the increase of Gd³⁺ ion doping concentration and reached the maximum when Gd³⁺ ion doping concentration was 30 mol%. Secondly, the relationship between the up-conversion luminescence performance and the excitation power of Gd³⁺ doping concentration of 30 mol% was further studied, and the excitation power was 0.5～1.5 W. The red and green upconversion luminescence intensity (R/G) ratio of LiGd_0.3Y_0.49F₄∶Yb³⁺/Ho³⁺ micron crystal only changes about 12% with the increase of excitation power. The upconversion luminescence of LiGd_0.3Y_0.49F₄∶Yb³⁺/Ho³⁺ micron crystal does not change obviously with the increase of excitation power, but still emits stable and bright green light. This phenomenon shows that incorporating Gd³⁺ ions greatly improves the up-conversion luminescence performance of the samples, and this stable and efficient luminescence performance guarantees its good anti-counterfeiting performance. Finally, LiYF₄∶Yb³⁺/Ho³⁺ micron crystal powder with Gd³⁺ ion doping concentration of 30 mol% was mixed with screen metal ink in a certain proportion to produce screen anti-counterfeiting ink, and then the anti-counterfeiting logo pattern of “Xi’an” was printed on the glass base by screen printing technology. After drying treatment, under the excitation of 980 nm laser, it emits bright and stable green visible light, and the anti-counterfeiting logo made has the characteristics of high luminous intensity, easy to identify and not easy to fall off, which can be widely used in the field of anti-counterfeiting.

Key words：Up-conversion luminescence; Li(Gd_xY_1-x)_0.79F₄∶Yb_0.2/Ho_0.01; Micron crystals; Hydrothermal synthesis method; Anti-counterfeiting identification; Screen printing

收稿日期: 2021-08-26 修订日期: 2022-03-01

中图分类号:

TB34

基金资助: 国家自然科学基金项目(61805199)，陕西省自然科学基金项目(2020JM-578)资助

作者简介: 王翀，1972年生，西安邮电大学电子工程学院副教授 e-mail: cw72@xupt.edu.cn

引用本文:

王翀，王景华，李冬冬，佘江波. 掺Gd³⁺的LiYF₄∶Yb³⁺/Ho³⁺微米晶体制备以及在防伪中的应用研究[J]. 光谱学与光谱分析, 2022, 42(11): 3581-3587.
WANG Chong, WANG Jing-hua, LI Dong-dong, SHE Jiang-bo. Preparation of Gd³⁺-Doped LiYF₄∶Yb³⁺/Ho³⁺ Micro-Crystal and the Application Research in Anti-Counterfeiting. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2022, 42(11): 3581-3587.

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