Thermally reversible γ-ray-induced redox reaction between substitutional iron and aluminum impurity centers in a silica glass

2001 ◽  
Vol 16 (1) ◽  
pp. 127-131 ◽  
Author(s):  
Radhaballabh Debnath
Keyword(s):  
Silica Glass ◽  
Γ Irradiation ◽  
Paramagnetic Resonance ◽  
Hole Trapping ◽  
Oxygen Hole ◽  
Before And After ◽  
Impurity Centers ◽  
Spin Resonances ◽  
Electron Paramagnetic ◽  
Hole Centers

The magnetic properties of the substitutional iron and aluminum impurity centers in a sintered Vycor silica glass were studied before and after 1.1–1.3 MeV γ irradiation. Observation of two overlapping spin resonances (g ∼ 4.20–4.28) in the spectra of both the irradiated and preirradiated glasses indicated the existence of two types of tetra coordinated substitutional iron centers of the [FeO4−/Na+]0 type. The intensity of these electron-paramagnetic resonance (EPR) signals decreased upon g irradiation of the glass with concomitant generation of aluminum hole center [AlO4]0, which was manifested by the occurrence of a new six-line EPR signal with g 4 2.009, while thermal annealing of these aluminum oxygen hole centers restores the intensity of the iron centers almost to their preirradiation level. This result suggests that if not the whole, a major fraction of the electrons released in the process of g-ray-induced hole trapping at the Al site are captured by the substitutional iron centers. The electron traps, thus formed, are quite stable and can be deactivated by thermal stimulation.

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

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.

Spectroscopic Evidence for the Formation of the Mercurous Ion in Irradiated Acetates

1971 ◽  
Vol 49 (17) ◽  
pp. 2868-2873 ◽  
Author(s):  
R. S. Eachus ◽  
F. G. Herring
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Optical Spectroscopy ◽  
Mercuric Acetate ◽  
Cadmium Acetate ◽  
Γ Irradiation ◽  
Paramagnetic Resonance ◽  
Spectroscopic Evidence ◽  
Acetate Trihydrate ◽  
Electron Paramagnetic ◽  
Mercurous Ion

The Hg(I) center has been produced by γ-irradiation both in Hg(II) doped cadmium acetate trihydrate and pure mercuric acetate. Both electron paramagnetic resonance and optical spectroscopy have been used to identify this species. The results indicate that the Hg(I) ion is produced in a covalent environment.

Luminescence and EPR Study of Lithium-Diffused ZnO Crystals

2002 ◽  
Vol 744 ◽  
Author(s):  
N. Y. Garces ◽  
Lijun Wang ◽  
M. M. Chirila ◽  
L. E. Halliburton ◽  
N. C. Giles
Keyword(s):  
Room Temperature ◽  
Deep Level ◽  
Chemical Vapor ◽  
Vapor Transport ◽  
Chemical Vapor Transport ◽  
Paramagnetic Resonance ◽  
Lithium Diffusion ◽  
Before And After ◽  
Electron Paramagnetic ◽  
Transport Method

ABSTRACTZinc oxide (ZnO) crystals grown by the seeded chemical vapor transport method have been studied using photoluminescence (PL), thermoluminescence (TL), and electron paramagnetic resonance (EPR) techniques. Lithium acceptors were diffused into the crystals during anneals in LiF powder at temperatures in the 750 to 850°C range. After a lithium diffusion, EPR was used to monitor neutral lithium acceptors and neutral shallow donors, as well as Ni3+, Fe3+, and Cu2+ impurities unintentionally present. Excitonic and deep-level PL emissions were also monitored before and after these diffusions. Two broad overlapping TL emission bands were observed at 117 and 145 K when a Li-diffused crystal was illuminated at 77 K with 325-nm light and then rapidly warmed to room temperature. The two TL bands have the same spectral dependence (the peak in wavelength is 540 nm when the intensity of the light reaches a maximum). These “glow” peaks occur when electrons are thermally released from Ni2+ and Fe2+ ions and recombine with holes at neutral lithium acceptors.

An Experimental Technique for Studying Chemisorption Reactions by Means of Electron Paramagnetic Resonance Spectroscopy

1972 ◽  
Vol 26 (2) ◽  
pp. 239-241 ◽  
Author(s):  
Eugene P. Scheide ◽  
George G. Guilbault
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Experimental Method ◽  
Electron Paramagnetic Resonance Spectroscopy ◽  
Cupric Chloride ◽  
Resonance Spectroscopy ◽  
Epr Spectrum ◽  
Paramagnetic Resonance ◽  
Before And After ◽  
Chemisorption Bond ◽  
Electron Paramagnetic

A new experimental method and a specially designed EPR cell are described for use in the study of chemisorption reactions. By studying the EPR spectrum of a surface both before and after chemisorption, it can be shown whether unpaired d electrons are used in the chemisorption bond and the nature of this bond. The EPR spectra of a cupric chloride surface, both before and after a gaseous ligand (diisopropyl methyl phosphonate) is chemisorbed, are shown and the results are interpreted in terms of the type of bond formed.

scholarly journals Structural and Optical Modifications in the BaO-ZnO-LiF-B2O3-Yb2O3 Glass System after γ-Irradiation

Materials ◽  
2021 ◽  
Vol 14 (22) ◽  
pp. 6955
Author(s):  
Nimitha S. Prabhu ◽  
Hiriyur Mallaiah Somashekarappa ◽  
M. I. Sayyed ◽  
Hamid Osman ◽  
Sultan Alamri ◽  
...  
Keyword(s):  
Trap Depth ◽  
Structural Rearrangement ◽  
Glass System ◽  
Γ Irradiation ◽  
Oxygen Hole ◽  
Spin Resonance ◽  
Before And After ◽  
Radiation Induced ◽  
The Fourier Transform ◽  
Induced Defects

A Yb3+-doped borate glass system was examined for the structural and optical modifications after γ-irradiation. Among the studied 10BaO-20ZnO-20LiF-(50-x)B2O3-xYb2O3 (x = 0.1, 0.5, 0.7, and 1.0 mol%) glasses, the 10BaO-20ZnO-20LiF-49.9B2O3-0.1Yb2O3 glass showed the highest thermoluminescence intensity, trap density, and trap depth. The glass was irradiated with the optimum γ-dose of 1 kGy towards the analysis of radiation-induced defects. The amorphous nature was preserved before and after irradiation. The glass density slightly increased after irradiation. The structural rearrangement was evident from the Fourier transform infrared spectroscopy by the appearance and disappearance of some bonds after γ-irradiation. The transformation of [BO4] units into [BO3] units and non-bridging oxygens was deduced. The color of the glass darkened after irradiation and the optical absorption intensity enhanced between 250 and 700 nm. The optical bandgap reduced and Urbach energy increased upon γ-dose exposure. The electron spin resonance of the irradiated glass exhibited two signals at g = 2.0167 and g = 1.9938, corresponding to the non-bridging oxygen hole center and Boron E’-center, respectively.

scholarly journals Epr Spectrum Angular Dependences In Liyf4 Crystal / Epr Spektru Leņķiskās Atkarības Liyf4 Kristālā

2012 ◽  
Vol 49 (6-I) ◽  
pp. 49-54
Author(s):  
A. Antuzevics ◽  
A. Fedotovs ◽  
U. Rogulis
Keyword(s):  
Room Temperature ◽  
Temperature Analysis ◽  
Epr Spectrum ◽  
Spectral Parameters ◽  
Paramagnetic Resonance ◽  
X Ray ◽  
Crystal Growth Process ◽  
Before And After ◽  
Impurity Ion ◽  
Electron Paramagnetic

Abstract Electron paramagnetic resonance (EPR) measurements have been made for two perpendicular planes in a LiYF4 crystal before and after x-ray irradiation at room temperature. Analysis of the EPR spectrum angular dependence shows the presence of two defects - an impurity ion, which was embedded during the crystal growth process, and an x-ray induced defect with the g-factor of approx. 2.0. Spectral parameters and possible defect models are discussed.

scholarly journals Electron Paramagnetic Resonance, and Thermoluminiscence Mechanism In Radiation Shielding Cr2O3 - Ba(La)2SiO6 Glasses

2021 ◽  
Author(s):  
RK GUNTU
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Mean Free Path ◽  
Mass Attenuation Coefficient ◽  
Radiation Shielding ◽  
Γ Irradiation ◽  
Paramagnetic Resonance ◽  
Protection Efficiency ◽  
Shielding Properties ◽  
Thermal Analysis Techniques ◽  
Electron Paramagnetic

Abstract The research on Cr2O3 doped SiO2 glasses is well known for advanced dielectrics. However, there are many other valuable properties associated with Cr2O3 inclusive various glasses. In this view, the current research aimed to develop the radiation shielding, elastically rich, and the EPR based Cr2O3 doped Ba(La)2SiO6 glass resource. Electron paramagnetic resonance, radiation shielding, and elastic studies have been employed to investigate the advanced characteristics. Structural characterization suggests glassy behavior with the Cr2O3 undoped glass. Whereas the other involved with Cr2O3 mol% shown with the ceramic behavior. The glass transition phenomena and forming abilities are studied with the help of differential thermal analysis techniques. Elastic studies have been done with the limit on the glasses, which suggests the glasses are flexible for elastic use. The electron paramagnetic resonance reports suggest high order of dipole-dipole super-exchange interaction and rhombohedral distortion within the glasses. Furthermore, we have tested the glasses for radiation shielding properties. The values of mass attenuation coefficient, radiation protection efficiency, mean free path, and energy absorption build-up factor of the glasses are measured and compared with values obtained with the help of standard photon shielding and dosimetry software. The studies indicate that the glasses developed are capable of radiation shielding. Upon 50 kGy, γ - irradiation, the thermoluminescence properties of the glasses are reported. The results found to be interesting, and reveal the resource developed are thermoluminescent at low activation energies. Furthermore, we have tested, the glasses for radiation shielding properties. Moreover, to introduce the detailed correlation between electron paramagnetic resonance, and thermoluminescence phenomenon, we have annealed the glasses under 0 to 300 oC temperature and upon the 0 to 50 kGy, γ - irradiation dose level. The electron paramagnetic resonance and thermoluminescence properties obtained for the glasses are highly correlative.

Microstructural Evolution of Pb(Zr,Ti)O3 Ceramics Using Electron Paramagnetic Resonance

1993 ◽  
Vol 310 ◽  
Author(s):  
W. L. Warren ◽  
B. A. Tuttle ◽  
R. W. Schwartz ◽  
W. F. Hammetter ◽  
D. C. Goodnow ◽  
...  
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Microstructural Evolution ◽  
Lead Zirconate Titanate ◽  
Perovskite Phase ◽  
Lead Zirconate ◽  
Solution Chemistry ◽  
Paramagnetic Resonance ◽  
Before And After ◽  
High Concentrations ◽  
Electron Paramagnetic

AbstractUsing electron paramagnetic resonance (EPR) we have followed the microstructural evolution with temperature of lead zirconate titanate (PZT) ceramics from the amorphous to the perovskite phase. A number of paramagnetic point defects were identified (Carbon, Pb+3, and Ti+3) while traversing the evolution of these ceramics during various heat treatments both before and after optical illumination. Perhaps the most important finding is that the Pb+3 and Ti+3 centers can only be optically created in the perovskite materials, thereby, showing that they are not associated with the amorphous or the pyrochlore phases. It is also found that EPR signals attributed to carbon radicals are present in fairly high concentrations (4 × 1017/cm3) if the solution chemistry derived PZT materials are annealed in an oxygen deficient ambient (0.1% O2) at 650°C.

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