Chinese Journal of Rare Metals

2026, v.50;No.366(09) 1513-1528

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Research Progress on Rare Earth Halide Scintillation Crystals

Shi Yanan;Jiang Zhouqing;Zhang Tianpeng;Wang Chenger;Gui Qiang;Zhang Chunsheng;Yu Jinqiu;

Abstract：

Scintillation crystals are a type of optical functional crystal material that can convert the energy of high-energy rays or particles such as X-rays,gamma rays,and neutrons into ultraviolet or visible pulsed light after absorption.As key materials for radiation detection,scintillation crystals show great application potential in fields such as nuclear medical imaging,high-energy physics,security inspection,and industrial non-destructive testing.In the past two decades,rare earth halide scintillation crystals have achieved rapid development due to their excellent properties such as high light yield,high energy resolution,and fast decay,becoming a research hotspot for new scintillation materials.Rare earth halide scintillation crystals mainly include two categories:one is the scintillation crystal with rare earth elements as the matrix material,such as crystals with optically inert ions La~(3+),Gd~(3+),Lu~(3+)and Y~(3+) as the matrix material,whose 4f electron orbits are either empty or full,making them suitable as the matrix material for scintillation crystals;the second is the doped scintillation crystal with rare earth ions as the luminescent center,such as the efficient 5d→4f transition of rare earth ions such as Ce~(3+)(4f~1),Eu~(2+)(4f~7),Pr~(3+)(4f~2) as the luminescent center of scintillation crystals.In view of the differentiated demand for scintillation crystal performance in different application scenarios,it is of great academic value and application prospect to carry out the material design and performance optimization research of new rare earth halide scintillation crystals.However,these crystals generally have the inherent defect of being easily deliquescent,which poses severe challenges to the preparation of high-purity anhydrous raw materials,crystal growth process control,and device processing and application,significantly increasing the difficulty and cost of their preparation.Based on the type of luminescent center,this paper divided rare earth halide scintillation crystals into three categories:Ce~(3+) activated,Eu~(2+) activated,and Pr~(3+) activated for review.It outlined the structural foundations and historical development of these materials,with a focused discussion on the scintillation mechanisms,growth techniques,performance optimization,high-purity precursor synthesis,and industrial applications pertaining to each category.Since the discovery of LaCl_3:Ce and LaBr_3:Ce crystals in the early 20th century,the research of rare earth halide scintillation crystals had entered a rapid development stage.A series of new scintillation crystal materials with high light yield,high energy resolution,fast decay,and even the ability to distinguish gamma rays and neutrons had emerged.The paper detailed Ce~(3+)-activated trivalent rare-earth halide and rare-earth/alkali metal composite halide scintillators,Eu~(2+)-activated alkali/alkaline earth metal halide and composite halide scintillators,and Pr~(3+)-activated trivalent rare-earth halide and rare-earth/alkali metal composite halide scintillators,covering their luminescence mechanisms,research history,crystal structure,chemical composition,performance,applications,and commercialization status.Current challenges and future directions were also analyzed.Extensive research indicated that fast scintillators with Ce~(3+)/Pr~(3+) as luminescent centers and microsecond-level slow scintillators with Eu~(2+) as luminescent centers both had promising application prospects.With the increasing demands for scintillator materials in different application fields,researchers had carried out extensive work in exploring new scintillation crystal material systems.Different application fields had their own emphases on the performance requirements of scintillation crystals.Optimizing the types and concentrations of rare earth activators and regulating their energy level relaxation and energy transfer processes was an effective way to improve the performance of scintillation crystal materials.The future research direction of rare earth halide scintillation crystals will mainly focus on:(1) developing new halide scintillation crystals with superior scintillation performance features such as ultra-high light yield,ultra-high energy resolution,ultra-fast decay,and multimode detection;(2) further enhancing the comprehensive performance of existing crystals,breaking through their large-size,high-quality crystal growth technology,reducing their overall cost,and expanding their commercial applications.In recent years,China had made significant progress in self-reliance in the field of rare earth halide scintillation crystals,especially in the industrialization technology level.The upstream high-purity anhydrous rare earth halide raw materials had basically achieved self-sufficiency.The midstream crystals like LaBr_3:Ce,CeBr_3,SrI_2:Eu,and Cs_2LiYCl_6:Ce(CLYC:Ce) had been commercialized,and their sizes and performances have basically reached the international equivalent level.In the downstream sectors,innovative applications had been realized in areas like space physics and advanced radiation detection equipment.With continuous progress across the entire industry chain,China is expected to achieve leapfrog development in this field and become a global leader in rare-earth halide scintillation crystals.

Key Words： rare earth;halide;doping;scintillation crystal;luminescent center

Abstract:

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Foundation: 国家重点研发计划项目（2022YFB3503601）资助

Authors: Shi Yanan;Jiang Zhouqing;Zhang Tianpeng;Wang Chenger;Gui Qiang;Zhang Chunsheng;Yu Jinqiu;

DOI: 10.13373/j.cnki.cjrm.XY25080007

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