Synthesis, Characterization and Study of the Radiation Effects on Hollandite Ceramics Developed for Cesium Immobilization

ABSTRACTProgress on separating the long-lived fission products has notably implied basic research on specific host matrices, especially for the immobilization of cesium. Barium hollandite (BaAl2Ti6O16) ceramics have received considerable interest because of their high cesium incorporation ability and chemical stability. This study deals with the preparation of hollandite in the BaxCsy(Al,Fe)2x+yTi8–2x-yO16 (x+y<2) compositional range by an oxide route. Different parameters such as the grain size of the precursor or the temperature and duration of sintering were changed in order to optimize ceramics synthesis. To estimate the hollandite radiation resistance, external electron irradiation experiments (simulating the β particles emitted by radioactive cesium) were performed on hollandite of simple composition. The irradiation-induced defects were studied by Electron Paramagnetic Resonance (EPR) spectroscopy and their nature is discussed.

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Radiation Effects on Hollandite Ceramics developed for Radioactive Cesium Immobilization

MRS Proceedings ◽

10.1557/proc-792-r2.3 ◽

2003 ◽

Vol 792 ◽

Author(s):

V. Aubin ◽

D. Caurant ◽

D. Gourier ◽

N. Baffier ◽

S. Esnouf ◽

...

Keyword(s):

Radiation Effects ◽

Liquid Waste ◽

Fission Products ◽

Radioactive Cesium ◽

Radioactive Liquid Waste ◽

Epr Spectrum ◽

Paramagnetic Resonance ◽

Γ Radiation ◽

The Stability ◽

High Level

ABSTRACTProgress on separating the long-lived fission products from the high level radioactive liquid waste (HLW) has led to the development of specific host matrices, notably for the immobilization of cesium. Hollandite (nominally BaAl2Ti6O16), one of the main phases constituting Synroc, receives renewed interest as specific Cs-host wasteform. The radioactive cesium isotopes consist of short-lived Cs and Cs of high activities and Cs with long lifetime, all decaying according to Cs+→Ba2++e- (β) + γ. Therefore, Cs-host forms must be both heat and (β,γ)-radiation resistant. The purpose of this study is to estimate the stability of single phase hollandite under external β and γ radiation, simulating the decay of Cs. A hollandite ceramic of simple composition (Ba1.16Al2.32Ti5.68O16) was essentially irradiated by 1 and 2.5 MeV electrons with different fluences to simulate the β particles emitted by cesium. The generation of point defects was then followed by Electron Paramagnetic Resonance (EPR). All these electron irradiations generated defects of the same nature (oxygen centers and Ti3+ ions) but in different proportions varying with electron energy and fluence. The annealing of irradiated samples lead to the disappearance of the latter defects but gave rise to two other types of defects (aggregates of light elements and titanyl ions). It is necessary to heat at relatively high temperature (T=800°C) to recover an EPR spectrum similar to that of the pristine material. The stability of hollandite phase under radioactive cesium irradiation during the waste storage is discussed.

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SiCCSiAntisite Pairs as Dominant Irradiation Induced Defects in p-Type 4H-SiC

Materials Science Forum ◽

10.4028/www.scientific.net/msf.615-617.357 ◽

2009 ◽

Vol 615-617 ◽

pp. 357-360 ◽

Cited By ~ 5

Author(s):

Uwe Gerstmann ◽

A.P. Seitsonen ◽

Francesco Mauri ◽

Hans Jürgen von Bardeleben

Keyword(s):

First Principles ◽

Density Functional ◽

Paramagnetic Resonance ◽

Functional Theory ◽

Radiation Induced ◽

P Type ◽

Induced Defects ◽

Electron Paramagnetic ◽

Irradiation Induced Defects ◽

Microscopic Origin

In this work we elucidate the microscopic origin of the dominant radiation induced I-II spectra in p-type doped 4H-SiC. By calculating the electronic g-tensor from first principles in the framework of density functional theory, basal antisite pairs SiCCSi + are shown to give rise to the characteristic anisotropic g-tensors found in the electron paramagnetic resonance (EPR) measurements. Additional central hyperfine (hf) splittings of about 100 MHz due to the SiC antisite nuclei are predicted theoretically and also resolved experimentally. We have, thus, identified antisite pairs as a dominant defect in electron and proton irradiated p-type doped 4H-SiC.

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Detection of electron paramagnetic resonance of radiation-induced defects in BaFBr via recombination luminescence

Radiation Effects and Defects in Solids ◽

10.1080/10420159908230134 ◽

1999 ◽

Vol 149 (1-4) ◽

pp. 69-72 ◽

Cited By ~ 1

Author(s):

U. Rogulis ◽

S. Schweizer ◽

J.-M. Spaeth

Keyword(s):

Electron Paramagnetic Resonance ◽

Recombination Luminescence ◽

Paramagnetic Resonance ◽

Radiation Induced ◽

Induced Defects ◽

Electron Paramagnetic

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Radiation-induced defects in montebrasite: An electron paramagnetic resonance study of O – hole and Ti3+ electron centers

American Mineralogist ◽

10.2138/am-2020-7168 ◽

2020 ◽

Vol 105 (7) ◽

pp. 1051-1059

Author(s):

José R. Toledo ◽

Raphaela de Oliveira ◽

Lorena N. Dias ◽

Mário L.C. Chaves ◽

Joachim Karfunkel ◽

...

Keyword(s):

Electron Paramagnetic Resonance ◽

Electron Irradiation ◽

Color Centers ◽

Hydroxyl Groups ◽

Γ Irradiation ◽

Paramagnetic Resonance ◽

Radiation Induced ◽

Induced Defects ◽

Electron Paramagnetic ◽

Hole Centers

Abstract Montebrasite is a lithium aluminum phosphate mineral with the chemical formula LiAlPO4(Fx,OH1–x) and considered a rare gemstone material when exhibiting good crystallinity. In general, montebrasite is colorless, sometimes pale yellow or pale blue. Many minerals that do not have colors contain hydroxyl ions in their crystal structures and can develop color centers after ionization or particle irradiation, examples of which are topaz, quartz, and tourmaline. The color centers in these minerals are often related to O− hole centers, where the color is produced by bound small polarons inducing absorption bands in the near UV to the visible spectral range. In this work, colorless montebrasite specimens from Minas Gerais state, Brazil, were investigated by electron paramagnetic resonance (EPR) for radiation-induced defects and color centers. Although γ irradiation (up to a total dose of 1 MGy) did not visibly modify color, a 10 MeV electron irradiation (80 MGy) induced a pale greenish-blue color. Using EPR, O− hole centers were identified in both γ- or electron-irradiated montebrasite samples showing superhyperfine interactions with two nearly equivalent 27Al nuclei. In addition, two different Ti3+ electron centers were also observed. From the γ irradiation dose dependency and thermal stability experiments, it is concluded that production of O− hole centers is limited by simultaneous creation of Ti3+ electron centers located between two equivalent hydroxyl groups. In contrast, the concentration of O− hole centers can be strongly increased by high-dose electron irradiation independent of the type of Ti3+ electron centers. From detailed analysis of the EPR angular rotation patterns, microscopic models for the O− hole and Ti3+ electron centers are presented, as well as their role in the formation of color centers discussed and compared to other minerals.

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