First Principles Calculations for Scintillation in Ce-Doped Y and La Oxyhalides

Chaudhry, A.; Canning, Andrew; Boutchko, Rostyslav; Porter-Chapman, Yetta D.; Bourret-Courchesne, Edith; Derenzo, Stephen E.; Grønbech‐Jensen, Niels

doi:10.1109/tns.2009.2013856

Cited by 14 publications

(8 citation statements)

References 16 publications

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“…So, we can expect luminosity to increase from YOF to YOI which supports the earlier reports. 5,6 Moreover, the width of the lower energy absorption band (or imaginary part of the dielectric function) increases from YOF to YOI because of which the number of electrons available for excitation also increases and leads to increased luminescence which also supports the earlier reports. This may be one of the reasons for the increase in the luminescence from YOF to YOI.…”

Section: Vibrational Propertiessupporting

confidence: 86%

“…6 In order to understand the underlying mechanism responsible for change in the luminescence, we have investigated the electronic and optical properties of the host compounds YOX (X ¼ F, Cl, Br, and I) particularly with the inclusion of excitonic effect which, as we shall show, plays a major role in these materials. The organization of the paper is as follows.…”

Section: Introductionmentioning

confidence: 99%

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Excitonic effects in oxyhalide scintillating host compounds

Shwetha

Kanchana

Valsakumar

2014

Journal of Applied Physics

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Electronic and elastic properties of yttrium gallium garnet under pressure from ab initio studiesAb-initio calculations based on density functional theory have been performed to study the electronic, optical, mechanical, and vibrational properties of scintillator host compounds YOX (X ¼ F, Cl, Br, and I). Semiempirical dispersion correction schemes are used to find the effect of van der Waals forces on these layered compounds and we found this effect to be negligible except for YOBr. Calculations of phonons and elastic constants showed that all the compounds studied here are both dynamically and mechanically stable. YOF and YOI are found to be indirect band gap insulators while YOCl and YOBr are direct band gap insulators. The band gap is found to decrease as we move from fluorine to iodine, while the calculated refractive index shows the opposite trend. As the band gap decreases on going down the periodic table from YOF to YOI, the luminescence increases. The excitonic binding energy calculated, within the effective mass approximation, is found to be more for YOF than the remaining compounds, suggesting that the excitonic effect to be more in YOF than the other compounds. The optical properties are calculated within the Time-Dependent Density Functional Theory (TDDFT) and compared with results obtained within the random phase approximation. The TDDFT calculations, using the newly developed bootstrap exchange-correlation kernel, showed significant excitonic effects in all the compounds studied here. V C 2014 AIP Publishing LLC. [http://dx.

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Section: Vibrational Propertiessupporting

confidence: 86%

Section: Introductionmentioning

confidence: 99%

Excitonic effects in oxyhalide scintillating host compounds

Shwetha

Kanchana

Valsakumar

2014

Journal of Applied Physics

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“…This trend was predicted by Chaudhry et al [32]. It exhibits broad unresolved emission from 400 to 650 nm with peak maximum at 470 nm.…”

Section: +supporting

confidence: 77%

“…Firstprinciple calculations reveal large Ce 3+ 4f-valence band gaps for YOF: Ce 3+ and LaOF: Ce 3+ . These gaps reduce the probability of cerium to trap holes, thereby decreasing the probability of cerium scintillation [32]. As a result, the luminescence observed under X-rays could be attributed to intrinsic luminescence from the host instead of cerium.…”

Section: +mentioning

confidence: 99%

Room-temperature scintillation properties of cerium-doped REOX (RE=Y, La, Gd, and Lu; X=F, Cl, Br, and I)

Eagleman

Bourret-Courchesne

Derenzo

2011

Journal of Luminescence

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The scintillation properties of cerium-doped oxyhalides following the general formula REOX (RE=Y, La, Gd, and Lu; X=F, Cl, Br, and I) are reported. These materials were synthesized under dry conditions as microcrystalline powders from conventional solid state reactions. The room temperature X-ray excited emission and scintillation decay curves were measured and analyzed for each material. Additionally, the hygroscopic nature of the oxychlorides and oxybromides was compared to that of their corresponding rare earth halides. The yttrium, lanthanum, and gadolinium oxychlorides, and all of the oxybromides and oxyiodides are found to be activated by Ce 3+ . GdOBr doped with 0.5% Ce 3+ has the highest light output with a relative luminosity of about one-half that of LaBr 3 : Ce 3+ . It displays a single exponential decay of 30 ns. Research Highlights►Room temperature scintillation properties of cerium doped rare earth oxyhalides. ►Oxybromides and oxyiodides most efficient scintillators. ►Cerium activation may be linked to structure.

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“…La 2 O 3 :Ce and LaAlO 3 :Ce, even though the Ce has slightly higher electronegativity than La. [14] Ab initio calculations based on density functional theory have been successfully used by our group [27][28][29] as well as by others [30,31] to study Ce 4f and 5d level locations in known scintillator and non-scintillator materials. In this paper, we present results from first-principles bandstructure calculation of Ce doped RE 2 M 2 O 7 class of compounds.…”

Section: Introductionmentioning

confidence: 99%

First-principles studies of Ce-doped RE2M2O7 (RE = Y, La; M = Ti, Zr, Hf): A class of nonscintillators

Chaudhry

Canning

Boutchko

et al. 2011

Journal of Applied Physics

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First-principles study of the electronic structure and optical properties of Ce-doped ZnOLanthanum and yttrium compounds with composition RE 2 M 2 O 7 (RE ¼ Y, La; M ¼ Ti, Zr, Hf) have high density and high Z and can be doped with Ce onto the La and Y sites. This makes these compounds good candidates for Ce-activated scintillator c-ray detectors particularly for the hafnate systems which have a very high density. There is disagreement in the literature concerning La 2 Hf 2 O 7 :Ce as it has been reported to show both bright as well as no Ce-activated luminescence by different experimental groups. We have performed first-principles electronic structure calculations of these compounds doped with Ce using the pseudopotential method based on the generalized gradient approximation in density functional theory. The positions of the Ce 4f states relative to the valence band maximum and the position of the Ce 5d states relative to the conduction band minimum (CBM) of the host material are determined. We find, unlike Ce-activated La and Y compounds where the CBM is typically of La 5d or Y 4d character, that in these systems the CBM is predominately of d character on the Ti, Zr, Hf atoms. For all these compounds, we also find that the Ce 5d state lies above the CBM which would prevent any luminescence from the Ce site.

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First Principles Calculations for Scintillation in Ce-Doped Y and La Oxyhalides

Cited by 14 publications

References 16 publications

Excitonic effects in oxyhalide scintillating host compounds

Excitonic effects in oxyhalide scintillating host compounds

Room-temperature scintillation properties of cerium-doped REOX (RE=Y, La, Gd, and Lu; X=F, Cl, Br, and I)

First-principles studies of Ce-doped RE2M2O7 (RE = Y, La; M = Ti, Zr, Hf): A class of nonscintillators

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