[Paper Review] The Characterization of new Eu2+ doped TlSr2I5 Scintillator Crystals

H. J. Kim, G. Rooh+3 more|arXiv (Cornell University)|Sep 9, 2017

Radiation Detection and Scintillator Technologies1 references3 citations

TL;DR

This study characterizes Eu2+-doped TlSr2I5 scintillator crystals grown via the two-zone vertical Bridgman method, demonstrating high light yield (70,000 ph/MeV) and excellent energy resolution (4.2% FWHM) at 662 keV using a 137Cs source. The material exhibits strong broad emission peaking at 463 nm with two decay components, making it a promising candidate for high-resolution X- and γ-ray spectroscopy due to its high effective Z (61) and density (5.30 g/cm³).

ABSTRACT

TlSr2I5: Eu2+ is a newly discovered scintillator and show promising scintillation properties for X- and γ-rays spectroscopy applications. Two zones vertical Bridgman technique is used for the growth of this scintillator. Luminescence properties of the grown crystals are measured under X-ray excitation at room temperature. Pure and Eu2+ doped crystals contained broad emission bands between 445-670 nm peaking at 528 nm and 430-600 nm peaking at 463 nm, respectively. Energy resolution, light yield and decay time profiles are studied under 662 keV γ-ray excitation using 137Cs radioactive source. Energy resolution of 4.2 % (FWHM) is obtained for 3 mol% Eu2+ doped crystal. For the same sample, light yield of 70,000 ph/MeV is also obtained. Three and two decay constants are observed for the pure and Eu2+ doped samples, respectively at room temperature. Effective Z-number and density are found to be 61 and 5.30 g/cm3, respectively.

Motivation & Objective

• To develop and characterize a new scintillator material, TlSr2I5:Eu2+, for high-energy radiation detection.
• To evaluate the luminescence properties of pure and Eu2+-doped TlSr2I5 crystals under X-ray excitation.
• To measure key scintillation parameters—light yield, energy resolution, and decay kinetics—under 662 keV γ-ray excitation.
• To determine the effective atomic number (Z_eff) and density to assess radiation detection potential.
• To establish the material’s suitability for X- and γ-ray spectroscopy applications through comprehensive performance evaluation.

Proposed method

• Growth of TlSr2I5:Eu2+ crystals using the two-zone vertical Bridgman technique to ensure high quality and uniformity.
• Measurement of photoluminescence emission spectra under X-ray excitation at room temperature to identify emission peaks.
• Irradiation with a 137Cs γ-ray source (662 keV) to evaluate scintillation performance under practical conditions.
• Analysis of decay time profiles using time-resolved spectroscopy to determine decay constants for pure and doped samples.
• Calculation of energy resolution (FWHM) from the 662 keV peak to assess spectroscopic performance.
• Determination of effective Z-number and density from elemental composition and crystal structure data.

Experimental results

Research questions

• RQ1 What is the luminescence emission spectrum and peak position of Eu2+-doped TlSr2I5 under X-ray excitation?
• RQ2 What is the light yield and energy resolution of TlSr2I5:Eu2+ under 662 keV γ-ray excitation?
• RQ3 How many decay components are present in the scintillation decay profile of the doped crystal at room temperature?
• RQ4 What is the effective Z-number and density of TlSr2I5:Eu2+, and how do they contribute to radiation detection efficiency?
• RQ5 How does Eu2+ doping affect the scintillation properties compared to the pure host crystal?

Key findings

• The Eu2+-doped TlSr2I5 crystal exhibits a broad emission band peaking at 463 nm under X-ray excitation.
• A light yield of 70,000 photons per MeV was achieved for the 3 mol% Eu2+ doped sample under 662 keV γ-ray excitation.
• An energy resolution of 4.2% (FWHM) was measured for the 3 mol% Eu2+ doped crystal at 662 keV, indicating high spectroscopic quality.
• Two distinct decay constants were observed in the scintillation decay profile of the Eu2+-doped crystal at room temperature.
• The effective Z-number of the crystal was calculated to be 61, and its density was 5.30 g/cm³, indicating high stopping power for γ-rays.
• The pure TlSr2I5 crystal showed a broad emission band peaking at 528 nm, while the Eu2+-doped version exhibited a blue-shifted peak at 463 nm.