Mg共掺杂Gd3(Al,Ga)5O12:Ce晶体快发光的作用机理

doi:10.15541/jim20210804

无机材料学报 ›› 2022, Vol. 37 ›› Issue (10): 1123-1128.DOI: 10.15541/jim20210804

Mg共掺杂Gd₃(Al,Ga)₅O₁₂:Ce晶体快发光的作用机理

李铭清¹^,²(), 王林伟², 丁栋舟²(), 冯鹤¹

1.上海大学材料科学与工程学院, 上海 200444
2.中国科学院上海硅酸盐研究所, 上海 201899

收稿日期:2021-12-29 修回日期:2022-02-16 出版日期:2022-10-20 网络出版日期:2022-07-08
通讯作者: 丁栋舟, 正高级工程师. E-mail: dongzhou_ding@mail.sic.ac.cn
作者简介:李铭清(1996-), 男, 硕士研究生. E-mail: mingqing114@foxmail.com
基金资助:
上海科学技术委员会项目(20511107400);国家自然科学基金(11475241)

Mechanism of Mg-codoping in Improving the Time Performance of Gd₃(Al,Ga)₅O₁₂:Ce Scintillator

LI Mingqing¹^,²(), WANG Linwei², DING Dongzhou²(), FENG He¹

1. School of Material Science and Engineering, Shanghai University, Shanghai 200444, China
2. Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 201899, China

Received:2021-12-29 Revised:2022-02-16 Published:2022-10-20 Online:2022-07-08
Contact: DING Dongzhou, professor. E-mail: dongzhou_ding@mail.sic.ac.cn
About author:LI Mingqing (1996-), male, Master candidate. E-mail: mingqing114@foxmail.com
Supported by:
Program of Shanghai Science and Technology Commission(20511107400);National Natural Science Foundation of China(11475241)

摘要/Abstract

摘要：

Gd₃(Al,Ga)₅O₁₂:Ce (GAGG:Ce)闪烁体综合性能优异, 应用前景广阔。为加快GAGG的发光衰减速度, 本研究通过提拉法生长了Mg共掺的Gd₃(Al,Ga)₅O₁₂:Ce单晶。测试结果显示, 随着Mg²⁺掺杂浓度增加, 晶体的闪烁衰减速度加快, 光输出降低。传统解释认为, Mg²⁺通过电荷补偿作用将部分Ce³⁺转换成Ce⁴⁺, 后者的发光速度更快。本研究尝试从缺陷的形成与抑制的角度来讨论Mg改善GAGG:Ce晶体闪烁性能的作用机理。由于Ce的离子半径比Gd大, Ce离子掺入将导致发光中心Ce_Gd附近的晶格发生畸变。畸变结果为近邻的八面体格位空间变大, 反位缺陷将更容易在这些变大的八面体格位形成。最终每个发光中心Ce_Gd被四个反位缺陷Gd_Al包裹, 后者捕获载流子, 延缓从基体到发光中心的能量传递, 导致发光速度变慢。由于Mg的离子半径介于Gd和Al之间, Mg_Al将更容易在上述畸变的八面体格位形成, 这会抑制反位缺陷Gd_Al在发光中心Ce_Gd附近形成(或富集), 最终降低(甚至消除)反位缺陷对发光中心的不良影响。XEL测试结果显示, 随着Mg掺杂量增大, 与反位缺陷相关的发射峰强度变弱, 这可以证明Mg对反位缺陷有抑制作用。

关键词: 闪烁体, GAGG:Ce, 反位缺陷, 衰减时间

Abstract:

With its excellent comprehensive performance, Gd₃(Al,Ga)₅O₁₂:Ce (GAGG:Ce) scintillation crystal has broad application prospects. To accelerate the luminescence decay rate, Mg-codoped Gd₃(Al,Ga)₅O₁₂:Ce single crystals were grown by Czochralski method. The test results show that with the concentration of Mg²⁺ increasing, the scintillation decay of the crystal accelerates and the light output decreases. The conventional interpretation suggests that Mg²⁺ could convert part of Ce³⁺ into Ce⁴⁺ through charge compensation, and the Ce⁴⁺ luminesces more quickly. This study tries to discuss the mechanism of Mg-codoping in GAGG:Ce crystals from the perspective of antisite defect. Since the ionic radius of Ce is larger than Gd, the doping of Ce ions leads to a distortion of the crystal lattice near the luminescence center Ce_Gd. As a result of the distortion, the space of the adjacent octahedral sites become larger, and the antisite defects are more likely to form in these larger octahedral sites. Eventually each luminescence center Ce_Gd is surrounded by four antisite defects Gd_Al, which would capture carriers and delay the energy transfer from the matrix to the luminescence center. As the ionic radius of Mg is between Gd and Al, Mg_Alalso prefers to form in those distorted octahedral sites, which inhibits the formation (or enrichment) of the antisite defect Gd_Alnear the luminescence center Ce_Gd, and eventually reduces (or even eliminates) the adverse effects of the antisite defect on the luminescence center. XEL results show that with the increase of Mg concentration, the emission peak related to the antisite defect becomes weaker, which indicates that Mg could inhibit the formation of the antisite defect.

Key words: scintillator, GAGG:Ce, antisite defect, decay time

中图分类号:

李铭清, 王林伟, 丁栋舟, 冯鹤. Mg共掺杂Gd₃(Al,Ga)₅O₁₂:Ce晶体快发光的作用机理[J]. 无机材料学报, 2022, 37(10): 1123-1128.

LI Mingqing, WANG Linwei, DING Dongzhou, FENG He. Mechanism of Mg-codoping in Improving the Time Performance of Gd₃(Al,Ga)₅O₁₂:Ce Scintillator[J]. Journal of Inorganic Materials, 2022, 37(10): 1123-1128.

图/表 10

图1 Gd3Al2.3Ga2.7O12:Ce,Mg晶体

Fig. 1 Photos of Gd3Al2.3Ga2.7O12:Ce,Mg crystals

图2 Gd3Al2.3Ga2.7O12:Ce,Mg晶体的透射谱

Fig. 2 Transmission spectra of Gd3Al2.3Ga2.7O12:Ce, Mg crystals

图3 GAGG:Ce,Mg晶体的多道能谱(a)和闪烁衰减曲线(b)

Fig. 3 Energy spectra (a) and scintillation decay curves (b) of Mg co-doped GAGG:Ce crystals

表1 GAGG:Ce, Mg晶体的相对光输出和闪烁衰减时间, 其中闪烁衰减时间通过单指数函数拟合得到

Table 1 Relative light yield and scintillation decay time values of the Mg co-doped GAGG:Ce crystals. Scintillation decay is approximated by a single-exponential function

Sample	Light yield/%	Decay time/ns
Mg-0	100	128.01
Mg-1	90.1	91.79
Mg-3	68.8	67.06

图4 闪烁晶体发光过程示意图

Fig. 4 Schematic diagram of the scintillating procedure

图5 GAGG:Ce,Mg晶体的吸收谱(a)和激发谱(b)

Fig. 5 Absorption spectra (a) and PL excitation spectra (b) of GAGG:Ce,Mg crystals Colorful figures are available on website

图6 LuAG:Ce中反位缺陷LuAl的浓度与Ce3+浓度的关系

Fig. 6 Concentration of antisite defect LuAl in single crystal LuAG:Ce vs Ce3+ concentration

图7 GAGG晶格中十二面体格位附近的结构示意图(a)及Ce掺杂导致十二面体和八面体格位发生畸变的示意图(b)

Fig. 7 Schematic of the structure near the dodecahedral site (a), and the distortion of dodecahedral and octahedral sites caused by Ce doping (b)

表2 部分阳离子的半径(配位数为6[20])

Table 2 Ionic radii of the cations (coordination number: 6[20])

Cation	Ionic radii/nm	Cation	Ionic radii/nm
Gd³⁺	0.0938	Na⁺	0.1020
Al³⁺	0.0535	Be²⁺	0.0450
Ga³⁺	0.0620	Mg²⁺	0.0720
Li⁺	0.0760	Ca²⁺	0.1000

图8 GAGG:Ce,Mg晶体的X射线激发发射谱(插图为反位缺陷GdAl/Ga相关的发射峰)

Fig. 8 X-ray excited luminescence spectra of GAGG:Ce,Mg crystals with the inset showing the GdAl/Ga-related emission peak Colorful figures are available on website

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Mg共掺杂Gd₃(Al,Ga)₅O₁₂:Ce晶体快发光的作用机理

Mechanism of Mg-codoping in Improving the Time Performance of Gd₃(Al,Ga)₅O₁₂:Ce Scintillator

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