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Polycrystalline Gd 3 Ga 3 Al 2 O 12 :Ce (GGAG:Ce) pellets with various codopants were prepared via solid-state synthesis and characterized by X-ray diffraction, radioluminescence (RL), photoluminescence (PL), reflectivity and PL decay measurements. GGAG:Ce pellets codoped with B and Ba were found to have higher RL intensity than pellets with other codopants, while Ca codoping improved the decay time but reduced the RL intensity. These results were strongly correlated with the performance of these codopants in GGAG:Ce single crystals. The light yield of the single crystals codoped with B or Ba was ∼15% higher than the light yield of the GGAG:Ce crystal without codoping, while Ca codoping in single crystals resulted in lower light yield but shorter scintillation decay time (43 ns vs. 56 ns). The consistent performance of these codopants in both matrix forms indicates that sintering pellets may be used as a simple cost effective technique to evaluate compositions for likely single crystal scintillator performance. [ABSTRACT FROM AUTHOR]

KCaI 3 :Eu single crystals exhibit favorable scintillation properties and have potential for use in domestic security applications requiring radioisotope identification. The anisotropic thermal expansion of the orthorhombic unit cell of this perovskite-type scintillator has been investigated using in-situ high temperature X-ray diffraction on powdered samples. Samples from single crystals of both pure and Eu-doped KCaI 3 grown by the Bridgman method were used for comparison. Expansion with temperature along the b -axis is greatest with an average linear coefficient of thermal expansion of ≈ (41–46) x 10 −6  K −1 resulting from the weaker bonding between alternating layers of K and Ca parallel to the b -axis. Thermal expansion in each of the KCaI 3 samples has the highest degree of anisotropy with respect to the b and c axis with ratio ᾱ b /ᾱ c of 1.4–1.5. Additionally, we identify the predominant cleavage plane in KCaI 3 as (0 -3 -1) based upon Laue reflection imaging. [ABSTRACT FROM AUTHOR]

The distorted-perovskite scintillator materials CsCaI 3 :Eu and CsSrBr 3 :Eu prepared as single crystals have shown promising potential for use in radiation detection applications requiring a high light yield and excellent energy resolution. We present a study using high temperature powder X-ray diffraction experiments to examine a deleterious high temperature phase transition. High temperature phases were identified through sequential diffraction pattern Rietveld refinement in GSAS II. We report the linear coefficients of thermal expansion for both high and low temperature phases of each compound. Thermal expansion for both compositions is greatest in the [0 0 1] direction. As a result, Bridgman growth utilizing a seed oriented with the [0 0 1] along the growth direction should be used to mitigate thermal stress. [ABSTRACT FROM AUTHOR]

In this paper we report on the scintillation properties of TlSr 2 I 5 doped with Eu2+, a novel thallium-containing high-resolution scintillator for gamma-ray spectroscopy. Small diameter, good quality crystals of TlSr 2 I 5 :Eu (TSI) with different Eu2+ concentrations were grown by the vertical Bridgman method. X-ray diffraction measurements show that single crystals of TSI belong to the monoclinic system with space group P2 1 /c. TlSr 2 I 5 has a density of 5.32 g/cm3 and effective Z of 60. The X-ray excited emission of Eu2+ doped TlSr 2 I 5 features a broad emission band peaking between 460–470 nm. The light yield of TlSr 2 I 5 crystal doped with 1% Eu2+ is measured to be ∼ 72,000 ph/MeV with an energy resolution of 2.8% at 662 keV. The scintillation decay time which is characteristic of Eu2+ shows two components, with ∼ 90% of the light in a ∼ 500 ns component and the rest in a longer component of ∼ 3 μ s. [ABSTRACT FROM AUTHOR]

• Mixed scintillator CeBr 3−x I x was investigated. • X-ray diffraction was used to determine the structure both phases that formed. • Five singled crystals were grown via the vertical Bridgman technique. • A light yield of >80,000 ph/MeV was measured for the grown crystal CeBr 2 I. CeBr 3 is an intrinsic scintillator that has promising performance capabilities such as 60,000 ph/MeV and ~4% energy resolution at 662 keV. It has been shown that halide mixing can improve the light yield of single halide scintillators. In this work we attempted to improve on CeBr 3 by creating a mixed halide composition CeBr 3−x I x. Analysis of melt-freeze samples revealed that the light yield of CeI 3 rapidly increases as bromine is substituted. Thirteen mm diameter crystals were grown using the vertical Bridgman technique, with x values between 0.03 and 1. The CeBr 2.5 I 0.5 crystal segregated into two sections, colorless and green, while the CeBr 2 I crystal was entirely green. X-ray diffraction analysis was used to identify the two phases. Decay time increased as iodine concentration increased. All colorless phase crystals reached <4.5% energy resolution at 662 keV and >65,000 ph/MeV, with the CeBr 2.94 I 0.06 crystal achieving 3.9% energy resolution at 662 keV. The green phase crystals both reached light yields of 78,000 ph/MeV, the highest ever recorded for a CeI 3 phase crystal. [ABSTRACT FROM AUTHOR]