The impact of strontium composition on thallium-doped cesium iodide scintillators

Abstract

Investigating new scintillators with more alternative methods has been an attractive topic for a long time. This work aims to study the impact of strontium composition on thallium-doped cesium iodide scintillators. There are three different composition ratios of cesium iodide and strontium iodide precursors of 99:1, 95:5, and 90:10 with the same thallium doping of 0.28 mol%. The EDS measurements analyzed the soluble Sr-compositions in these grown crystals as 0%(undetectable), 0.43%, and 2.31%, respectively. With slightly increased strontium composition, the crystallite size was slightly smaller from 59.17, 45.51, to 33.23 nm, respectively. Moreover, the crystals have a somewhat more compressive strain and a slightly higher single crystallinity when the composition of strontium iodide increases. By analyzing the crystals' optical properties, the luminescent properties were trivially enhanced with a bit higher scintillation light yielding up to 29,859 photon/MeV of the crystal with a Sr-composition of 2.31%. Photoluminescence measurements exhibit the enhanced 520 nm scintillation and the lower 410 nm emission at higher Sr contents. These crystals’ emission decay times were obtained as τ1 = 500 ns (fast component) and τ2 = 700 ns (slow component) and slightly slower times with a higher Sr content. Lastly, radiation detection efficiency has been investigated at various energy levels of gamma rays from Am-241, Co-57, Ba-133, and Cs-137 sources. We found that the crystal with a higher Sr composition of 2.31% has better energy resolutions down to the best one of 7.9% at 662-keV measurement. In summary, higher strontium codoping with thallium in cesium iodide scintillators can enhance the crystal structure and optical properties. This would be one candidate of the promising scintillators for developing alternative high-performance radiation detectors for high-speed imaging applications.