Toward High Energy Resolution in CsSrI3/Eu2+ Scintillating Crystals: Effects of Off-Stoichiometry and Eu2+ Concentration

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• 作者：Yuntao Wu ; Sasmit S. Gokhale ; Adam C. Lindsey ; Mariya Zhuravleva ; Luis Stand ; Jesse Ashby Johnson II ; Matthew Loyd ; Merry Koschan ; Charles L. Melcher
• 刊名：Crystal Growth & Design
• 出版年：2016
• 出版时间：December 7, 2016
• 年：2016
• 卷：16
• 期：12
• 页码：7186-7193
• 全文大小：664K
• ISSN：1528-7505

文摘

CsSrI₃/Eu²⁺ has very promising scintillation properties for gamma-ray spectroscopy applications, but it has proven difficult to grow high quality single crystals in large sizes. This paper reports a composition-engineering strategy, in this case a combination of off-stoichiometric melts and Eu²⁺ concentration optimization, to obtain large-size CsSrI₃/Eu²⁺ crystals with excellent energy resolution. Crystals of a series of off-stoichiometric compositions, Cs_(1+x)(Sr,Eu)_(1–x)I_(3–x) (x = 0, 0.05, 0.06, and 0.1), were grown by the Bridgman method. The Cs_1.06Sr_0.94I_2.94/Eu²⁺ single crystal has the highest optical transmittance between 450 and 800 nm. Cs_1.06Sr_0.94I_2.94 single crystals doped with 0.5, 1, 3, 5, and 7 mol % Eu²⁺ ions were also grown by the Bridgman method. The effects of Eu²⁺ concentration on the phase purity and optical and scintillation properties were studied. X-ray diffraction patterns confirmed the phase purity of all samples with the exception of a hydrate phase formed during measurement. Increasing Eu²⁺ concentration leads to longer decay components due to the effect of self-absorption. An unexpected relationship was found between the Eu²⁺ concentration and the appearance of two photopeaks in a pulse height spectrum acquired under a single gamma-ray energy of 662 keV irradiation. The origins of this phenomenon are proposed from experimental insights. The optimal composition we developed achieved an excellent energy resolution of 3.4% for ϕ22 mm × 2 mm, 3.9% for ϕ22 mm × 15 mm, and 4.1% for ϕ22 mm × 19 mm at 662 keV. The results of this paper lead to a better understanding of the effects of composition-engineering in optimization of nonstoichiometric scintillator compounds.