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Local coordination state of rare earth in eutectic scintillators for neutron detector applications.

Masai H, Yanagida T, Mizoguchi T, Ina T, Miyazaki T, Kawaguti N, Fukuda K - Sci Rep (2015)

Bottom Line: In this work, we examine optical properties of Eu-doped 80LiF-20CaF2 eutectics for neutron detector applications based on the Eu distribution.However, transparency, which depends on an ordered lamellar structure, is found to be important for a high light yield in neutron detection.The results confirm the effectiveness of the basic idea concerning the separation of radiation absorbers and activators in particle radiation scintillation and present potential for further improvement of novel bulk detectors.

View Article: PubMed Central - PubMed

Affiliation: Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan.

ABSTRACT
Atomic distribution in phosphors for neutron detection has not been fully elucidated, although their ionization efficiency is strongly dependent on the state of the rare earth in the matrix. In this work, we examine optical properties of Eu-doped 80LiF-20CaF2 eutectics for neutron detector applications based on the Eu distribution. At low concentrations, aggregation of Eu cations is observed, whereas homogeneous atomic dispersion in the CaF2 layer, to substitute Ca(2+) ions, is observed in the eutectics at high concentrations. Eu LIII edge X-ray absorption fine structure (XAFS) analysis suggests that neutron responses do not depend on the amount of Eu(2+) ions. However, transparency, which depends on an ordered lamellar structure, is found to be important for a high light yield in neutron detection. The results confirm the effectiveness of the basic idea concerning the separation of radiation absorbers and activators in particle radiation scintillation and present potential for further improvement of novel bulk detectors.

No MeSH data available.


Related in: MedlinePlus

XANES analysis of Eu-doped LiF/CaF2 eutectics.(a) Eu- LIII edge XANES spectra of 0.1Eu- and 5Eu- doped LiF/CaF2 eutectics along with the deconvoluted fitting lines. Circles, solid lines, and dashed lines indicate the raw data, fitting curves, and each component, respectively. (b) Eu2+/Eu3+ ratio and Eu2+ amount as a function of Eu concentration.
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f4: XANES analysis of Eu-doped LiF/CaF2 eutectics.(a) Eu- LIII edge XANES spectra of 0.1Eu- and 5Eu- doped LiF/CaF2 eutectics along with the deconvoluted fitting lines. Circles, solid lines, and dashed lines indicate the raw data, fitting curves, and each component, respectively. (b) Eu2+/Eu3+ ratio and Eu2+ amount as a function of Eu concentration.

Mentions: Although emission of Eu2+ is usually observed by neutron irradiation, the Eu2+/Eu3+ ratio should be clarified because the starting material is EuF3. In order to calculate the Eu2+/Eu3+ ratio in the total Eu concentration, X-ray absorption fine structure (XAFS) analysis of Eu LIII edge is performed. Figure 4(a) shows Eu- LIII edge X-ray absorption near edge structure (XANES) spectra of 0.1 Eu- and 5Eu- doped LiF/CaF2 eutectics along with the deconvoluted fitting lines. Circles, solid lines, and dashed lines indicate the raw data, fitting curves, and each component, respectively. When comparing the present spectra with previous papers2425 and that of EuF3 shown in Supplementary Fig. 6, the lower absorption is due to Eu2+ whereas the higher one is due to Eu3+. Figure 4(b) shows the Eu2+/Eu3+ ratio and the Eu2+ amount of these eutectics as a function of Eu concentration. The Eu2+/Eu3+ ratio drastically decreases with increasing total Eu concentration, and less than 10% of Eu cations exist as Eu2+ in the 5 mol%-doped sample. On the contrary, the amount of Eu2+, which is obtained by multiplication of the total Eu concentration and the Eu2+/Eu3+ ratio, increases. Generally, many secondary electrons (typically several tens of thousands of electrons) in the host are generated by the 6Li(n, α)3H reaction in the neutron irradiation process due to interactions with charged particles. Therefore, we can conclude that an effective radiative efficiency of the Eu centre is prevented in samples containing higher concentrations of Eu.


Local coordination state of rare earth in eutectic scintillators for neutron detector applications.

Masai H, Yanagida T, Mizoguchi T, Ina T, Miyazaki T, Kawaguti N, Fukuda K - Sci Rep (2015)

XANES analysis of Eu-doped LiF/CaF2 eutectics.(a) Eu- LIII edge XANES spectra of 0.1Eu- and 5Eu- doped LiF/CaF2 eutectics along with the deconvoluted fitting lines. Circles, solid lines, and dashed lines indicate the raw data, fitting curves, and each component, respectively. (b) Eu2+/Eu3+ ratio and Eu2+ amount as a function of Eu concentration.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4544017&req=5

f4: XANES analysis of Eu-doped LiF/CaF2 eutectics.(a) Eu- LIII edge XANES spectra of 0.1Eu- and 5Eu- doped LiF/CaF2 eutectics along with the deconvoluted fitting lines. Circles, solid lines, and dashed lines indicate the raw data, fitting curves, and each component, respectively. (b) Eu2+/Eu3+ ratio and Eu2+ amount as a function of Eu concentration.
Mentions: Although emission of Eu2+ is usually observed by neutron irradiation, the Eu2+/Eu3+ ratio should be clarified because the starting material is EuF3. In order to calculate the Eu2+/Eu3+ ratio in the total Eu concentration, X-ray absorption fine structure (XAFS) analysis of Eu LIII edge is performed. Figure 4(a) shows Eu- LIII edge X-ray absorption near edge structure (XANES) spectra of 0.1 Eu- and 5Eu- doped LiF/CaF2 eutectics along with the deconvoluted fitting lines. Circles, solid lines, and dashed lines indicate the raw data, fitting curves, and each component, respectively. When comparing the present spectra with previous papers2425 and that of EuF3 shown in Supplementary Fig. 6, the lower absorption is due to Eu2+ whereas the higher one is due to Eu3+. Figure 4(b) shows the Eu2+/Eu3+ ratio and the Eu2+ amount of these eutectics as a function of Eu concentration. The Eu2+/Eu3+ ratio drastically decreases with increasing total Eu concentration, and less than 10% of Eu cations exist as Eu2+ in the 5 mol%-doped sample. On the contrary, the amount of Eu2+, which is obtained by multiplication of the total Eu concentration and the Eu2+/Eu3+ ratio, increases. Generally, many secondary electrons (typically several tens of thousands of electrons) in the host are generated by the 6Li(n, α)3H reaction in the neutron irradiation process due to interactions with charged particles. Therefore, we can conclude that an effective radiative efficiency of the Eu centre is prevented in samples containing higher concentrations of Eu.

Bottom Line: In this work, we examine optical properties of Eu-doped 80LiF-20CaF2 eutectics for neutron detector applications based on the Eu distribution.However, transparency, which depends on an ordered lamellar structure, is found to be important for a high light yield in neutron detection.The results confirm the effectiveness of the basic idea concerning the separation of radiation absorbers and activators in particle radiation scintillation and present potential for further improvement of novel bulk detectors.

View Article: PubMed Central - PubMed

Affiliation: Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan.

ABSTRACT
Atomic distribution in phosphors for neutron detection has not been fully elucidated, although their ionization efficiency is strongly dependent on the state of the rare earth in the matrix. In this work, we examine optical properties of Eu-doped 80LiF-20CaF2 eutectics for neutron detector applications based on the Eu distribution. At low concentrations, aggregation of Eu cations is observed, whereas homogeneous atomic dispersion in the CaF2 layer, to substitute Ca(2+) ions, is observed in the eutectics at high concentrations. Eu LIII edge X-ray absorption fine structure (XAFS) analysis suggests that neutron responses do not depend on the amount of Eu(2+) ions. However, transparency, which depends on an ordered lamellar structure, is found to be important for a high light yield in neutron detection. The results confirm the effectiveness of the basic idea concerning the separation of radiation absorbers and activators in particle radiation scintillation and present potential for further improvement of novel bulk detectors.

No MeSH data available.


Related in: MedlinePlus