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Single crystals of Eu2+-activated SrI2, one of the most leading-edge scintillators for gamma-ray spectroscopy applications, have a low radioactive background, excellent energy resolution of 2.6%–3% at 662 keV, and high light yield of 80 000–120 000 photons/MeV. In this article, tetravalent ions codoping, namely, Hf4+ codoping, was used to enhance its scintillation performance. $\emptyset 12$ mm diameter SrI2:Eu2+ single crystals codoped with 0, 0.05, 0.1, and 0.2 at% Hf4+ were successfully grown by the multiampoule Bridgman method. All grown crystals are highly transparent, crack-free, and inclusion-free. The effects of Hf4+ codoping concentration on the optical and scintillation properties were studied. The gamma-ray energy resolutions of SrI2:Eu single crystals can be improved from 3.4% to 3.1% at 662 keV, and from 6.6% to 6.0% at 122 keV upon 0.05 at% Hf4+ codoping. [ABSTRACT FROM AUTHOR]

In this study, we demonstrated a drastic improvement in energy resolution of (Lu0.75Y0.25)3Al5O12:Pr (LuYAG) single crystal scintillators from 4.8% to 4.1% at 662 keV upon Li+ codoping, which is the best value ever reported in the class of oxide single crystal scintillators. Li+ codoping can also significantly enhance its scintillation yield from 16 000 to 25 000 photons MeV−1, but slightly prolong the scintillation decay time. As Li+ codoping was found to have a negligible effect on the light yield non‐proportionality, we attributed the significant improvement in energy resolution to the reduced statistical variance in the number of photoelectrons produced in the photomultiplier tube (Rstat). [ABSTRACT FROM AUTHOR]

Cerium-doped YAlO3:Ce (YAP:Ce) is an interesting oxide scintillator that exhibits a wider range of light yield nonproportionality on a sample-to-sample basis than most other well-known oxide scintillators. In general, most oxide materials, such as Bi4Ge3O12 and Lu2SiO5:Ce, are thought to have an intrinsic proportional response that is nearly constant between samples and independent of growth conditions. Since light yield nonproportionality is responsible for degrading the achievable energy resolution of all known scintillators, it is important to understand what contributes to the behavior. In an attempt to understand if the phenomenon can be affected by growth parameters or by other means, seven samples of YAP:Ce were collected from various sources, and eight samples were grown in-house using the Czochralski method. Based on optical and scintillation measurement as well as direct measurement of the cerium concentration, it was determined that the light yield proportionality in YAP:Ce is strongly related to the cerium concentration. Samples that were found to have higher relative cerium concentration displayed a more proportional light yield response. In addition, it was determined that samples with higher cerium concentration also exhibit a faster decay time and an enhanced energy resolution when compared to samples with less cerium. It was also determined that growth in a reducing atmosphere can effectively suppress a parasitic optical absorption band. [ABSTRACT FROM PUBLISHER]

Codoping is an effective approach for precise control of point defects in many advanced materials, and can be used to optimize their function. This paper reports an effort toward tailoring the scintillation properties of metal halides through defect engineering. A study of aliovalent codoping of the KCaI3:Eu2+ single‐crystalline scintillators is performed, through which it is discovered that a simultaneous suppression of X‐ray induced afterglow and improvement of gamma‐ray energy resolution can be successfully achieved via Zr4+ codoping. The afterglow level is reduced by more than twofold with Zr4+ codoping. The energy resolution of a 5 mm cubic KCaI3:Eu2+ sample is improved from 3.25 to 2.7% at 662 keV, and 6.5 to 5.73% at 122 keV upon Zr4+ codoping. Physical explanations for the improvements are revealed from our investigations into both the electronic structure and thermodynamics of the defects by using thermoluminescence techniques and density functional theory calculations. The codoped Zr4+ ions prefer to form interstitials acting as shallow electron traps. The {ZrCa+VCa} complex can co‐exist with Zri interstitials as shallow hole traps under certain condition, which are able to trap holes temporarily. [ABSTRACT FROM AUTHOR]

In this paper, nine different samples of \ YAIO3:{\ {Ce}} have been collected and analyzed. The light yield non-proportionality of each sample was measured and used to classify each sample as proportional or non-proportional. A variety of scintillation and optical measurements were conducted on each sample, and the proportional samples were generally found to have a higher light output and better energy resolution. In addition, a strong linear correlation was found between scintillation decay time and the degree of non-proportionality. Based on absorption measurements as well as radioluminescence data, it was determined that the non-proportional samples all shared a range of increased absorption near the cerium 5d absorption edge between about 325 and 400 nm. The increased absorption has been reported in literature, and it is believed to be the result of a material defect introduced during growth. Thermoluminescence glow curves were measured for two representative \ YAIO3:{\ {Ce}} samples, one from each proportionality grouping, and it was determined that there was an observable change in defect structure, but there were no additional traps visible in the glow curves of either the proportional or non-proportional samples. However, the intensity of the 105 K thermoluminescence peak was found to be approximately a factor of two greater in the non-proportional samples. Since the lifetime of this peak is known to be between 25 and 81 ns, it was determined to be the likely cause of the slower decay in the non-proportional samples. [ABSTRACT FROM PUBLISHER]

This paper investigates the effects of boron and calcium co-doping on the measured energy resolution of Gd3Ga3Al2O12:Ce (GGAG: Ce). For this study, three samples of GAGG were grown using the Czochralski method. The first sample was doped with Ce^3+ and was used as a reference for comparison. The next two samples were additionally doped with either B^3+ or Ca^2+. The boron co-doped sample was found to have an overall improved performance when compared to the reference sample. The light output of the GGAG:Ce,B was measured to be 10% greater than the reference sample. In addition, the sample was found to have less charge trapping and a more linear relative light yield response. These factors led to an observed improvement in energy resolution from 9% in the reference sample to 7.8% in the B^3+ co-doped sample. Co-doping with Ca^2+ led to an overall reduction in charge trapping; however, the sample suffered a 30% reduction in light output, and it was found to have a less linear relative light yield than the reference sample. Its energy resolution was measured to be 10.1%. The relationship between the measured energy resolution and the other measured properties in these samples is discussed. [ABSTRACT FROM AUTHOR]

Inch-sized scintillating crystals are required for practical radiation detectors such as hand-held radio-isotope identification devices. In this work, a transparent and colorless 2-inch diameter KCa 0 . 8 Sr 0 . 2 I 3 : 0 . 5 mo % E u 2 + single crystal was grown by the vertical Bridgman method, and the scintillation properties of a ∅ 50 mm × 45 mm long sample were evaluated. The Eu 2 + 5 d 1 - 4 f emission under X-ray excitation is centered at 472 nm. Its scintillation decay time under 137 Cs source irradiation is 2 . 37 μ s , and the absolute light output is 51,000 ± 3000 photons/MeV. The energy resolution at 662 keV was evaluated for different orientations of the crystals with respect to the PMT, and the effect of 40 K background subtraction on energy resolution was evaluated. The performance of the packaged crystal was also investigated. [ABSTRACT FROM AUTHOR]