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Title: Influence of Li-codoping on the radiation hardness of CsBr:Eu{sup 2+}

Abstract

The poor radiation hardness of the otherwise excellent x-ray storage phosphor CsBr:Eu{sup 2+} constitutes a problem for its commercial application in medical diagnostics. X-ray induced vacancy centers such as M-centers enhance the diffusion of Eu{sup 2+} activators resulting in a formation of photostimulated luminescence (PSL) inactive europium clusters or second phases of europium compounds. The present study investigates the influence of Li-codoping on the radiation hardness of CsBr:Eu{sup 2+}. It is reported that the integration of Li{sup +} into the CsBr:Eu{sup 2+} suppresses the generation of M-centers during x-irradiation and thereby partially improves the radiation hardness.

Authors:
; ; ; ;  [1];  [2]
  1. Department of Electronic Materials, Institute of Materials Science, Darmstadt University of Technology, 64287 Darmstadt (Germany)
  2. (Germany)
Publication Date:
OSTI Identifier:
20979417
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 101; Journal Issue: 11; Other Information: DOI: 10.1063/1.2743731; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; CESIUM BROMIDES; CRYSTALS; DIFFUSION; EUROPIUM COMPOUNDS; EUROPIUM IONS; HARDNESS; LITHIUM IONS; M CENTERS; PHOSPHORS; PHOTOLUMINESCENCE; X RADIATION

Citation Formats

Zimmermann, J., Hesse, S., Seggern, H. von, Fuchs, M., Knuepfer, W., and Siemens AG, Medical Solutions, Vacuum Technology, 91058 Erlangen. Influence of Li-codoping on the radiation hardness of CsBr:Eu{sup 2+}. United States: N. p., 2007. Web. doi:10.1063/1.2743731.
Zimmermann, J., Hesse, S., Seggern, H. von, Fuchs, M., Knuepfer, W., & Siemens AG, Medical Solutions, Vacuum Technology, 91058 Erlangen. Influence of Li-codoping on the radiation hardness of CsBr:Eu{sup 2+}. United States. doi:10.1063/1.2743731.
Zimmermann, J., Hesse, S., Seggern, H. von, Fuchs, M., Knuepfer, W., and Siemens AG, Medical Solutions, Vacuum Technology, 91058 Erlangen. Fri . "Influence of Li-codoping on the radiation hardness of CsBr:Eu{sup 2+}". United States. doi:10.1063/1.2743731.
@article{osti_20979417,
title = {Influence of Li-codoping on the radiation hardness of CsBr:Eu{sup 2+}},
author = {Zimmermann, J. and Hesse, S. and Seggern, H. von and Fuchs, M. and Knuepfer, W. and Siemens AG, Medical Solutions, Vacuum Technology, 91058 Erlangen},
abstractNote = {The poor radiation hardness of the otherwise excellent x-ray storage phosphor CsBr:Eu{sup 2+} constitutes a problem for its commercial application in medical diagnostics. X-ray induced vacancy centers such as M-centers enhance the diffusion of Eu{sup 2+} activators resulting in a formation of photostimulated luminescence (PSL) inactive europium clusters or second phases of europium compounds. The present study investigates the influence of Li-codoping on the radiation hardness of CsBr:Eu{sup 2+}. It is reported that the integration of Li{sup +} into the CsBr:Eu{sup 2+} suppresses the generation of M-centers during x-irradiation and thereby partially improves the radiation hardness.},
doi = {10.1063/1.2743731},
journal = {Journal of Applied Physics},
number = 11,
volume = 101,
place = {United States},
year = {Fri Jun 01 00:00:00 EDT 2007},
month = {Fri Jun 01 00:00:00 EDT 2007}
}
  • In this study, the photostimulated luminescence of the CsBr:Eu{sup 2+} needle image plates (NIPS) after vacuum ultraviolet (VUV) irradiation and their photoluminescence under VUV and UV excitation were investigated. It was shown that the photostimulable storage centers arise almost exclusively due to irradiation of the CsBr:Eu NIPs in the spectral lines of creation of the 4p{sup 5}5s anion excitons, and not in the region of interband transitions of CsBr. The explanation of the results is based mainly on the radiative and nonradiative decay of the self-localized e+Br{sub 2}{sup -} excitons.
  • The x-ray storage-phosphor CsBr:Eu{sup 2+} has been found to exhibit a strong increase in photostimulated-luminescence (PSL) intensity following hydration at room temperature. The sensitivity increases by a factor of 25 following a 60 min exposure to an atmosphere of 99% relative humidity, which is considered to be due to an incorporation of H{sub 2}O molecules within the CsBr:Eu{sup 2+} matrix, which are orientated by and enhance the electric fields surrounding (Eu{sup 2+}-O{sup 2-})-dipoles, increasing their charge trapping cross sections. Following irradiation the PSL increase is accompanied by the formation of mobile V{sub K}-centers, which decrease the F-center population by amore » recombination process, which appear as an intrinsic 360 nm emission from the CsBr matrix in low temperature thermoluminescence measurements.« less
  • CsBr:Eu{sup 2+} needle image plates exhibit an electron-paramagnetic-resonance (EPR) spectrum at room temperature (RT), whose intensity is correlated with the photostimulated luminescence sensitivity of the plate. This EPR spectrum shows a strong temperature dependence: At RT it is owing to a single Eu{sup 2+} (S =7/2) center with axial symmetry, whereas at T<35 K the spectra can only be explained when two distinct centers are assumed to be present, a minority axial center and a majority center with nearly extremely rhombic symmetry. In this paper these low-temperature centers are studied with electron nuclear double resonance (ENDOR) spectroscopy, which reveals themore » presence of {sup 1}H nuclei close to the central Eu{sup 2+} ions in the centers. Analysis of the angular dependence of the ENDOR spectra allows to propose models for these centers, providing an explanation for the observed difference in intensity between the spectral components and for their temperature dependence.« less
  • A new yellow pigment with the pyrochlore structure Ca[sub x]Y[sub 2[minus]x]O[sub 7] was prepared as a substitute for the decreasing variety of available yellow ceramic pigments due to the severe regulation of toxic lead and cadmium. The solubility limit of vanadium in this pigment was found to be 1.5 wt% as V[sub 2]O[sub 5] or 0.13 as x in the above formula expression. Characterization of vanadium in the vanadium pyrochlore yellow pigment by electron spectroscopy for chemical analysis and electron spin resonance showed that the oxidation state of vanadium was V[sup 5+] and its yellow color mostly originated from V[supmore » 5+] substituted for Ti[sup 4+]. Comparison of color characteristics of Ca[sub x]Y[sub 2[minus]x]V[sub x]Ti[sub 2[minus]x]O[sub 7] with those of commercial V-SnO[sub 2] and V-ZrO[sub 2] revealed that Ca[sub x]Y[sub 2[minus]x]V[sub x]Ti[sub 2[minus]x]O[sub 7] had better color strength and brightness than the commercial pigments.« less
  • (Y{sub 0.95}Eu{sub 0.05}){sub 2}O{sub 3} red phosphors are synthesized in one step via Ar/O{sub 2} thermal plasma oxidation of atomized alcohol solutions of the component nitrates. Phase structure analysis found the direct products to be mixtures of a cubic and monoclinic phases, and the powder collected from the wall part of the plasma reactor as well as the finer portion of the total powder have significantly higher monoclinic contents ({approx}55 and 71 wt%, respectively). An almost pure-cubic structured phosphor powder can be converted from the phase mixture by annealing at a minimum temperature of 900 Degree-Sign C for 12 h,more » but at the expenses of significant coarsening/sintering of the nano-sized particles. It was first shown that codoping with 20 at% of Sc{sup 3+} may effectively retard crystallization of the undesired monoclinic phase and thus yield phosphor powders of high specific surface area ({approx}21.7 m{sup 2}/g) and significantly improved 611-nm red emission. Formation mechanism of the monoclinic phase and the effects of Sc{sup 3+} codoping on phase structure and luminescence properties were discussed. - Graphical abstract: Y{sub 2}O{sub 3}:Eu phosphors are synthesized in one-step via thermal plasma processing. The direct products are monoclinic and cubic phase mixtures, and Sc{sup 3+} codoping effectively suppresses crystallization of the undesired monoclinic phase to yield phosphor powders of high specific surface area and significantly improved photoluminescence. Highlights: Black-Right-Pointing-Pointer Thermal plasma processing yields Y{sub 2}O{sub 3}:Eu phosphors in one-step. Black-Right-Pointing-Pointer The direct products are monoclinic and cubic phase mixtures. Black-Right-Pointing-Pointer Sc{sup 3+} codoping effectively suppresses monoclinic crystallization. Black-Right-Pointing-Pointer Better luminescence is achieved via Sc{sup 3+} codoping.« less