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In this paper, Φ25 mm lanthanum bromide scintillation crystals with 5%Ce3+ and different Sr2+ doping concentrations (0.1%, 0.3%, 0.5% in molar ratio) were successfully grown by spontaneous nucleation vertical Bridgman method. X-ray excited emission spectra, transmission spectra and pulse height spectra of these crystals were measured. Results show that, the emission spectra waveform of LaBr3:Ce crystals with different Sr2+ doping concentrations is basically consistent under X-ray excitation, and the emission peak shows a significant red shift compared with that of sample without Sr2+ doping. With the increase of Sr2+ doping concentration, the emission peak of LaBr3:Ce,Sr crystal shows a slight red shift. There is no obvious absorption peak range from 350 to 800 nm of LaBr3:Ce,Sr crystals with different Sr2+ doping concentrations. Compared with LaBr3:Ce crystals, transmittance of 0.3% and 0.5% Sr2+ doped LaBr3:Ce crystals decrease. In addition, with the increase of Sr2+ doping concentration, the energy resolution of the crystal increases correspondingly. LaBr3:Ce,0.5% Sr crystal has the highest energy resolution of 2. 99%@662 keV. The energy resolution of the encapsulated LaBr3:Ce,0.5%Sr crystal with size of Φ25 mm x 25 mm is 2.93%@662 keV. [ABSTRACT FROM AUTHOR]

The growth and scintillation properties of undoped and Ce 3+ -doped GdI 3 crystals were reported in this paper. These GdI 3 :χ%Ce (χ = 0, 1, 2) crystals were grown by the vertical Bridgman growth technique in evacuated quartz crucibles. X-ray excited optical luminescence spectra of GdI 3 :Ce exhibit a broad emission band (450 nm–650 nm) peaking at 520 nm corresponding to 5d 1 →4f 1 transition of Ce 3+ while the undoped GdI 3 crystal consists of a broad band (400 nm-600 nm) and several sharp lines peaking at 462 nm, 482 nm, 492 nm, 549 nm, 579 nm owing to the impurities ions and defects. The excitation spectra of Ce 3+ doped GdI 3 consist of two broad bands between 300 nm and 500 nm corresponding to 4f 1 →5d 1 absorption of Ce 3+ . The other absorption peaking at 262 nm in the spectrum of GdI 3 :2%Ce is assigned to band-to-band exciton transition. The excitation spectrum of undoped GdI 3 contains a flat absorption band from 330 to 370 nm and a broad band between 390 and 450 nm peaking at 414 nm corresponding to the absorption of the unintentionally doped Ce 3+ , Dy 3+ , Ho 3+ impurities and other defects. The emission spectrum of undoped GdI 3 under 332 nm excitation has the identical line peaks with the spectrum measured under X-ray excitation. The emission spectra of GdI 3 :2%Ce and GdI 3 :1%Ce show a broad band in the range of 450–750 nm with the maximum at 550 nm corresponding to 5d 1 →4f 1 transitions of Ce 3+ ion. The GdI 3 , GdI 3 :1%Ce and GdI 3 :2%Ce show fast principle decay time constant 73 ns, 69 ns and 58 ns respectively, besides, the undoped also shows a slow decay constant 325 ns which doesn't appear in Ce 3+ -doped GdI 3 crystal. The energy resolutions of GdI 3 :χ%Ce (χ = 1, 2) measured at 662 KeV are about 3%–5% and the undoped GdI 3 is 13.3%. [ABSTRACT FROM AUTHOR]

Eu 2+ :CeBr 3 crystals were grown by vertical Bridgman growth method and slight aliovalent doping of Eu 2+ in the CeBr 3 crystal did not change the crystal structure. The X-ray stimulated luminescence, photoluminescence, decay kinetics and scintillation properties were investigated at room temperature. The X-ray stimulated luminescence spectra exhibited wide broad emission bands from 3.54 eV to 2.95 eV in the Eu 2+ :CeBr 3 crystal with high content of 620 ppm of Eu 2+ , which were the overlap of the emission bands ascribed to 5d → 4f transition of Ce 3+ and 4f 6 5 d 1 → 4f 7 transition of Eu 2+ , respectively. When the content of Eu 2+ was decreased to 70 ppm, another emission band centered at 2.29 eV was observed. The photoluminescence spectra showed the energy transfer from Ce 3+ to Eu 2+ . This decreased the Ce 3+ emission intensity but enhanced the Eu 2+ emission intensity. The photoluminescence decay time of Ce 3+ emission decreased from 14 ns to 10 ns when the content of Eu 2+ increased from 70 ppm to 620 ppm. The decay time of the emission of 525 nm did not change with the excitation wavelength and Eu 2+ content, which could be assigned to the excitons that were bound on Eu 2+ related centers. The light output of the Eu:CeBr 3 crystal under the excitation of 241 Am radioactive source was less than 20.2% of Tl:NaI crystal. [ABSTRACT FROM AUTHOR]