Growth and Characterization of SrI₂:Eu Crystals Fabricated by the Czochralski Method

Abstract

This work presents the Czochralski growth of SrI2:Eu scintillation crystals. SrI2:Eu is among the brightest recently discovered scintillators with an excellent energy resolution for spectroscopic identification of radioactive isotopes. The Czochralski crystal growth method is optimal from the point of scaling up of crystal production with minimal investment into upgrade of crystal growth equipment. In this study SrI2:Eu crystals with the diameter of up to 50 mm were produced by the developed process based on the Czochralski method. The crystals are prone to cracking, and thermal fields in the crystallizer still should be optimized. Nevertheless the scintillation parameters of detectors cut from the grown crystals are similar to that in detectors fabricated by the conventional Bridgman-Stockbarger technology. The Eu2+ activator concentration across the crystals is uniform within 5%, as well as the energy resolution, which ranges within 3.6±0.1% at 662 keV. Also, the decay times under X-rays, and non-proportionality of scintillation light yield on excitation energy in the range of 31-1274 keV have been determined.

Growth and scintillation performances of SrI2:Eu with low activator concentration

“…7). These values are in the qualitative agreement with the data on decay times in dependence on activator Eu concentration in SrI2:Eu reported in [9,12], and confirm the reduction of the self-absorption phenomena in weakly doped crystals. Note the significant pileup observed in the 0.1 Eu% sample due to an increase of the carrier diffusion distance to activator centers at X-ray excitation.…”

“…Reduced amount of impurities in the feedstock eliminates the need to maintain large concentrations of EuI2. Similar scintillation parameters obtained in crystals grown from equally prepared raw materials using the Bridgman-Stockbarger method in this work and Czochralski [9] (see Fig. 6) indicate that the properties of SrI2:Eu do not depend on the crystal growth method.…”

“…As EuI2 likely can play a role of both luminescence activator, and admixture scavenger in halide melts [10,11], it was assumed that lower Eu content can satisfy the required properties when using raw materials of the optimized quality. To check and confirm the result obtained with Czochralski crystals [9], and to exclude the factor of crystal growth method, in this work SrI2:Eu crystals were grown in the concentration range of 0.1-5.5%…”

“…It was shown [9] that with an optimized raw material preparation procedure [2] and the activator content of around 0.5% Eu a high energy resolution of 3.5% can be achieved in SrI2:Eu crystals grown by the Czochralski technique. As EuI2 likely can play a role of both luminescence activator, and admixture scavenger in halide melts [10,11], it was assumed that lower Eu content can satisfy the required properties when using raw materials of the optimized quality.…”

Needs, Trends, and Advances in Inorganic Scintillators

“…• The growth of that material has been demonstrated by the Czochralski technique [64] for diameter up to 50 mm [see Fig. 5…”