Structure and scintillation of Eu2+-activated calcium bromide iodide

Abstract

Courchesne, Structure and scintillation of Eu 2 þ -activated calcium bromide iodide, Journal of Luminescence, http://dx. AbstractWe report the structure and scintillation properties of Eu 2+ -activated calcium bromide iodide. CaBr 0.7 I 1.3 was the only composition that could be synthesized in the CaBr 2 -CaI 2 system. The compound has an effective atomic number of 47 and crystallizes in a trigonal crystal system with the R-3 space group and a density of 3.93 g/cc. The structure is layered and contains Ca in an octahedral environment with the Br/I anions jointly occupying a single site. Eu 2+ -activated samples show an intense narrow emission, characteristic of the 5d-4f transition of Eu 2+ , when excited with UV or X-rays. The sample with 0.5% Eu shows a light output of 63,000 ph/MeV at 662 keV with 96% of the light emitted with a monoexponential decay time of 1,332 ns. An energy resolution of 10.4% full width at half maximum (FWHM) has been achieved for 662 keV gamma rays at room temperature.

Effects of increasing size and changing europium activator concentration in KCaI3 scintillator crystals

“…Light yield is shown to rise sharply with the addition of 0.2 % Eu and reaches a plateau of 70,000 -75,000 ph/MeV between dopant concentrations of 0.5 -5.0%. The small drop in light yield at 5.0% Eu is similarly observed in the investigation of CaI 2 :Eu whereby light yield was shown to decrease above 6% Eu concentration as well as for the investigation of Ca(BrI) 2 :Eu in which a small decrease in light yield was observed at 5% Eu [6]. This trend may suggest concentration quenching may be significant in this region and further dopant addition is expected to decrease the light yield further.…”

“…This approach is famously paralleled by the rediscovery of SrI 2 :Eu whereby the pioneering efforts of Hofstadter in the 1960's were revisited by increasing the Eu additions in the SrI 2 matrix from a maximum of 16,000 ppm (1.6 at%) specified in the patent [2] to upwards of 3-6 at% Eu now used today which has been shown to produce a 2-3 fold increase in light yield and improvement of the energy resolution to below 3% at 662 keV [3]. Similarly, the scintillation performance dependence with changing Eu activator concentrations in Ca containing host crystals can be found in recent reports on CaI 2: Eu, CaBr 2 :Eu, and Ca(BrI) 2 :Eu [4][5][6]. One drawback shared with these compounds arises from the highly layered structure of the CaX 2 matrix (X=Br,I) which has been shown to exhibit a mica-like cleavage behavior which makes fabrication of high quality single crystal monoliths quite difficult.…”

Nanocomposite Phosphor Consisting of CaI2:Eu2+ Single Nanocrystals Embedded in Crystalline SiO2

“…For the unindexed peaks in the searching for constituent elements of (CaI 2 :Eu 2+ /SiO 2 ), we were unable to find any substances registered in the Inorganic Crystal Structure Database. Rietveld refinement of the XRD pattern indicated that the unindexed peaks originated from a CaI 2 polytype that had a CdCl 2 -type structure ( thr notation: 6 H ) and was different from the previously reported polytype with a CdI 2 -type structure (2 H ). , The formation of a 6 H polytype has previously been achieved by substitution of Br at some of the I sites (CaI 1.3 Br 0.7 ) . The lattice parameters and space groups of 2 H -CaI 2 and 6 H -CaI 2 :Eu 2+ (Eu atom % = 0, 0.03, and 0.06 consisted in (CaI 2 :Eu 2+ /SiO 2 )) are listed in Table S3.…”

Defect chemistry of Eu dopants in NaI scintillators studied by atomically resolved force microscopy

“…The moire pattern indicates that the precipitate is a 2D sheet, weakly bound to the substrate. We propose a structural model based on I-Eu-I trilayers: The related materials like CaI 2 [6,37] or CdI 2 [38] have such layered bulk 5a), where the trilayers are weakly coupled together. Similar layered structures are also common for many transition metal halides [39].…”