Irradiated Crystals Research Articles

Electron paramagnetic resonance study of the paramagnetic centers in gamma-irradiated 2-nitrobenzoic acid single crystal

2-nitrobenzoic acid (C7H5NO4) (2NBA) single crystals were made paramagnetic using 60Co-gamma rays. An attempt was made to detect the resonance form formed in 2-nitrobenzoic acid single crystal with Electron Paramagnetic Resonance (EPR) Spectroscopy. EPR spectra were taken at 125 K in three different axes of the crystal. As a result of EPR analysis of gamma irradiated 2NBA single crystal, it was understood that 2NBA anion radical was formed. The principal values of the hyperfine structure constants, the principal values of the g-tensor and their direction cosines were calculated.

Microstructural investigation of Au ion-irradiated Eu-doped LaPO4 ceramics and single crystals

Ceramics and single crystals of LaPO4 monazite doped with Eu(III) were irradiated with 14 MeV Au5+ ions at three different fluences. Changes to crystallinity, local coordination environments, and topography were probed using grazing-incidence X-ray diffraction (GIXRD), vertical scanning interferometry (VSI), scanning electron microscopy (SEM), Raman, and luminescence spectroscopy. GIXRD data of the ceramics revealed fluence dependent amorphization. A similar level of amorphization was detected for samples irradiated with 5 × 1013 ions/cm2 and 1 × 1014 ions/cm2, whereas the sample irradiated with the highest fluence of 1 × 1015 ions/cm2 appeared slightly less amorphous. VSI showed clear swelling of entire grains at the highest ion fluence, while more localized damage to grain boundaries was detected for ceramic samples irradiated at the lowest fluence. Single crystal specimens showed no pronounced topography changes following irradiation. SEM images of the ceramic irradiated at the highest fluence showed topological features indicative of grain surface melting. Raman and luminescence data showed a different degree of disorder in polycrystalline vs. single crystal samples. While changes to PO4 vibrational modes were observed in the ceramics, changes were more subtle or not present in the single crystals. The opposite was observed when probing the local Ln-O environment using Eu(III) luminescence, where the larger changes in terms of an elongation of the Eu-O (or La-O) bond and an increasing relative disorder with increasing fluence were observed only for the single crystals. The dissimilar trends observed in irradiated single crystals and ceramics indicate that grain boundary chemistry likely plays a significant role in the radiation response.

Damage kinetics in high-temperature irradiated Ni crystals

High-temperature (∼800 K) ion irradiation with 380 keV Ar ions was used to modify the surface of Ni single crystals in order to generate radiation defects and mimic the effect of neutrons avoiding sample activation. The modified 800 nm thick layer was analyzed regarding structural and mechanical properties utilizing a combination of experimental and simulation techniques. The ion implantation fluence ranged from 1 × 1014 cm−2 up to 1 × 1016 cm−2, which corresponds to values of displacements per atom from 0.25 to 25, respectively. The structural characterization was performed by Rutherford Spectroscopy in Channeling mode (RBS/C) associated with scanning (SEM) and transmission electron microscopy (TEM). The experimental results were supported by Monte Carlo (McChasy) and Molecular Dynamics (MD-LAMMPS) simulations. The simulations performed using the second generation of the McChasy code show that the influence of bubbles formed inside the material is not negligible and affects the quantitative analysis of defects in the simulated spectra. A second step in damage kinetics was revealed for the highest dose (i.e., 25 dpa) as a consequence of the entanglement of dislocations and agglomeration of noble gas bubbles, which was confirmed by TEM analysis. Moreover, nanomechanical results confirm that Ar bubbles deteriorate mechanical properties such as hardness.

Temperature Dependent near Infrared Spectroscopy of Electron Irradiated Ceria Single Crystals.

The FTIR absorption bands of virgin and electron-irradiated CeO2 single crystals were measured from 20 K to 500 K between 4000 cm-1 and 12,000 cm-1 (~830 nm to 2500 nm). Three broad bands centered at about 6100 cm-1 (~0.75 eV), 7000 cm-1 (~0.87 eV), and 10,500 cm-1 (~1.3 eV) were recorded above 100 K for the 2.5 MeV electron energy. Two smaller bands at about 4300 cm-1 (~0.53 eV) and 5500 cm-1 (~0.68 eV) were also recorded below 100 K. Similar broad bands centered at about 4100 cm-1 (~0.52 eV), 6400 cm-1 (~0.79 eV), 7600 cm-1 (~0.94 eV), and 10,500 cm-1 (~1.3 eV) are also found for the 1.4 MeV electron energy above 300 K. The evolution of these absorption bands was followed as a function of temperature. The plots of band intensity ratios show a thermally activated process corresponding to the ionization of the deep electronic levels of point defects in the band gap of ceria of ~26,000 cm-1 (~3.2 eV). These five bands are assigned to the different charge states (0, -1, -2, -3, -4) of the Ce vacancies produced by elastic collisions above 1.0 MeV.

Influence of swift heavy ions irradiation on optical and luminescence properties of Y3Al5O12 single crystals

Optical and luminescence properties of Y3Al5O12 (YAG) single crystals preliminary irradiated by swift heavy ions were studied. Swift heavy Xe ions with fluences ranging from 6·1010 to 2·1012 ions/cm2 were utilized for the irradiation of nominally undoped YAG single crystals. A stable strong induced absorption observed in the 200–600 nm spectral range correlates with the irradiation fluence. It is suggested that several centers are responsible for this induced absorption in YAG single crystals and their possible origin (F-type centers) is proposed and discussed. The swift heavy ions irradiation strongly modifies the luminescence properties of YAG, namely, the excitonic emission at liquid helium temperature is drastically suppressed in heavily irradiated crystals.

On the theory of nucleation of coherent inclusions in irradiated crystals

Based on a critical analysis of the existing model for the effect of excess vacancies and interstitials on the nucleation of coherent particles under irradiation, a new nucleation model is developed that uses the Brailsford-Bullough model for the steady state occupation probabilities of vacancies and interstitials at the particle interface, recently refined by the author. It is shown that, depending on the surface tension γ of a coherent particle, the nucleation mechanism can be qualitatively different. In the case of a relatively small γ, an instability can arise in the irradiated solid solution leading to the barrier-free nucleation of coherent precipitates. In the opposite case of a relatively large γ, the classical one-dimensional theory of homogeneous nucleation is applicable. In order to eliminate the uncertainty in the magnitude of surface tension (from the literature) and to better understand the underlying mechanisms of coherent particle nucleation in irradiation tests, additional atomistic studies are recommended.

Photochromic luminescence of organic crystals arising from subtle molecular rearrangement

Photoluminescence (PL) colour-changing materials in response to photostimulus play an increasingly significant role in intelligent applications for their programmability. Nevertheless, current research mainly focuses on photochemical processes, with less attention to PL transformation through uniform aggregation mode adjustment. Here we show photochromic luminescence in organic crystals (e.g. dimethyl terephthalate) with PL varying from dark blue to purple, then to bright orange-red, and finally to red. This change is attributed to the emergence of clusters with red emission, which is barely achieved in single-benzene-based structures, thanks to the subtle molecular rearrangements prompted by light. Crucial to this process are the through-space electron interactions among molecules and moderate short contacts between ester groups. The irradiated crystals exhibit reversible PL transformation upon sufficient relaxation, showing promising applications in information storage and smart optoelectronic devices. This research contributes to the development of smart photochromic luminescent materials with significant PL colour transformations through molecular rearrangement.

Detection of fluorescent low-energy proton tracks in lithium fluoride crystals

The exploitation of visible radiophotoluminescence in lithium fluoride (LiF) crystals, due to local aggregate point defects produced by ionizing radiation in the crystal lattice, is demonstrated for fluorescent imaging of single tracks of protons at low energies. LiF crystals were irradiated perpendicularly with respect to nearly monochromatic, collimated proton beams at the energies of about 1 MeV in a fluence range from ∼5.8 × 105 p/cm2 up to ∼3.4 × 107 p/cm2 and of about 2.6 MeV in a fluence range from ∼9.6 × 105 p/cm2 up to ∼4.7 × 106 p/cm2. The fluence values were estimated by detecting and automatically counting the tracks on the images acquired with a fluorescence microscope at high magnification; they were found to be in agreement with those obtained using CR39 plastic detectors irradiated under the same experimental conditions. Despite the very short range in matter of these charged particles, by focusing the excitation blue light at discrete depths in the irradiated LiF crystals, an estimate of the proton energies was also obtained. These first results are encouraging for the utilization of LiF crystals as fluorescent nuclear track detectors under typical conditions employed in ion radiobiology.

Absorption Band at 1600 cm-1 in the IR Spectra of Irradiated MgO Crystals

In the IR spectra of nominally pure and doped MgO crystals after irradiation, an intense absorption band appears at 1600 cm-1. This message discusses the model of the corresponding absorption center.

Optical properties of pure and Sn-doped β-Ga2O3 single crystals grown by optical float zone technique

High-quality single crystals of both pure and Sn:β-Ga2O3 single crystals weregrown using the optical floating zone technique and a comprehensive study of its luminescence and scintillation properties was carried out. The pure and Sn:β-Ga2O3 grown crystals were oriented along (100) by Laue diffraction pattern and its monoclinic structure was confirmed using a single crystal XRD. X-ray induced luminescence spectrum shows a maximum emission peak at 365 nm. The cut off wavelength was observed around 258 nm and the optical band gap was calculated to be 4.64 eV from UV–Vis-NIR transmission spectroscopy. The room temperature Raman spectra were recorded and the various vibration modes were investigated. Low temperature (10 to 300 K) and high temperature (325 to 675 K) TL measurements were carried out on X-ray irradiated crystals and its TL kinetic parameters such as activation energy (eV) and frequency factor (S) were calculated. Scintillation decay time profiles were measured for both pure and Sn-doped crystals under 137Cs γ-ray excitation. The calculated scintillation light output is 2300 Ph/5.5 Mev for Sn:β-Ga2O3 crystal under α-particle excitation from 241Am radiation source.

Hybrid density functional theory calculations for surface damaged phosphate products of laser irradiated KDP crystals

Surface damage products cause more UV absorption and increase surface damage compared to KDP crystals.

Investigations on gamma ray irradiated CMTC single crystals for opto-electronic application

Investigations on gamma ray irradiated CMTC single crystals for opto-electronic application

INFLUENCE OF ELECTRON IRRADIATION ON THE CRYSTAL STRUCTURE, SURFACE MICRORELIEF AND BANDGANP WIDTH OF THE TRIPLE CRYSTALS OF IRON DOPED MONOSELINIDE OF THALLIUM AND INDIUM

In this work, the effect of electron irradiation on the structure, surface morphology and band gap of single-and polycrystalsof iron-doped ternary crystals of thallium and indium monoselinides was investigated. It has been established that the synthesized polycrystalline samples, as well as the grown single crystals of thallium and indium monoselinides, are single-phase. The crystals have a tetragonal unit cell (space group I4/mcm) with the following lattice parameters: a ~ b = 8.12 Å, c = 6.88 Å, α=β=γ= 90°. Irradiation with electrons with an energy of 2 MeV and a beam current density of 0.085 μA/cm2leads to changes in the structure and properties of crystals in a complex manner depending on the electron fluence. Leads to a change in the parameters of the crystal lattice, an increase in the maximum value of the arithmetic mean deviation of the profile, as well as a decrease inthe height of the average surface roughness of the irradiated crystals. Irradiation of a powder sample with electrons with a fluence of 5x1016electron/cm2helps to increase the size of nanocrystallites from 32.50 nm to 43.33 nm.

ТАЛШЫҚТЫ-ОПТИКАЛЫҚ БАЙЛАНЫС ЖОЛДАРЫ НЕГІЗІНДЕ ЭНЕРГИЯ ТАРАТУ ЖҮЙЕСІНІҢ ЗЕРТХАНАЛЫҚ ҮЛГІСІН ӘЗІРЛЕУ ЖӘНЕ ЗЕРТТЕУ

In this article, a laboratory sample of an energy transmission system over a fiber-optic communication line is being developed and investigated, which makes it possible to provide power to autonomous ultra-low-power electronic devices located at a considerable distance from energy sources. The system being developed will make it possible to abandon the use of copper conductors and batteries for autonomous stationary devices, which is associated with certain difficulties from the point of view of technical implementation. The result of this study is a developed laboratory sample that allows measuring the values of current and voltage in the branch of the photodetector. The method of an equivalent generator was used, as well as the well-known laws of a circuit with two dedicated nodes for an active two- pole. When analyzing the literature, scientific achievements and discoveries in the field of research, a proprietary research concept was formulated that differs from foreign analogues. During the experiment, the photodetector was in idle, short-circuit mode and was connected to a high-resistance load. Based on experimental data, volt-ampere characteristics (VAC) were constructed using a radiation source (laser) with a power of 10 and 30 MW. The technical parameters and characteristics of the radiation source and the irradiated silicon crystal are given. The output electrical power is determined using the laws of electrical engineering, including Ohm's law. To process the results obtained, quadratic interpolation of the function, the results of the root-mean-square approximation were used, and regression analysis was also performed. Absolute and relative errors were calculated. The student's coefficient was determined with a confidence interval of 0.95. According to the results of the study, the efficiency of a laboratory sample of an energy transmission system over a fiber-optic communication line was determined.

Power supply via fiber-optical conductor for sensors of mine working monitoring system

The article describes a system of power transmission via fiber-optic cable, which allows the supply of power to sensors and other electronic devices of ultra-low power located in places of mining workings, for which the mandatory requirement is fire safety. The developed system will allow to replace the application of copper conductors. The result of this research is the developed laboratory bench that allows measuring the current and voltage parameters in the photodetector branch. The equivalent generator method has been used, as well as the known circuit laws with two dedicated nodes for an active two-terminal network. When analyzing the literature, the existing scientific achievements, and discoveries in the field of research, an own concept of research has been formed that is different from foreign analogs. During the experiment, the studies have been performed when the photodetector was in the short circuit, idle mode, and connected to a high-resistance load. Based on the results obtained, current-voltage characteristics (CVC) and histograms have been built using a radiation source (laser) with a power of 10 and 30 mW. The parameters and technical characteristics of the irradiated silicon crystal and the radiation source have been given. The obtained electrical power has been determined using the known laws of electrical engineering, including the Ohm law. To process the experimental data, there has been used quadratic interpolation of the function, the results of the root-mean-square approximation, and there has been carried out the regression analysis. Absolute and relative errors have been calculated. The Student coefficient has been determined with a confidence interval of 0.95. Based on the results of the study, the efficiency of the power transmission system has been determined

FORMATION OF DEFECTS IN THE ANION AND CATION SUBLATTICE OF MgAl<sub>2</sub>O<sub>4</sub> CRYSTALS IRRADIATED BY HIGH ENERGY XENON IONS

In this work, the optical characteristics of an aluminum-magnesium spinel irradiated with 220 MeV Xe ions, which simulate the effect of nuclear fuel fission fragments were studied. During the experiments, the transmission spectra were measured in the IR region (240–12500) cm−1, the optical absorption spectra in the range (2–7) eV, the Raman spectra were measured by the ion penetration depth, from the surface to 30 µm. In the optical absorption spectrum (2–8) eV of irradiated spinel crystals, a wide complex band of radiation-induced absorption is observed with a peak in the region of 5.3 eV associated with electronic color centers of the F + and F type, and hole color centers are responsible for optical absorption at ~ (3–4) eV. In the near IR region, the crystal retains its transparency. In the Raman spectrum, in addition to the Raman modes characteristic of an ideal crystal, additional modes, A1g* (720 cm−1), and Eg* (385 cm−1), appear mainly in the form of an asymmetric shoulder of the main Eg mode. As the depth increases, the A1g*/Eg ratio increases, reaching a maximum value of 0.05 at 6 µm, and remains practically unchanged until the end of the Xe ion range of 14 µm, and with a further decrease to 0.045 at a depth of 30 µm. That is, when irradiated with 220 MeV Xe ions, cation mixing occurs along the ion path.

Optical Characteristics of MgAl2O4 Single Crystals Irradiated by 220 MeV Xe Ions.

In In this study, the optical properties of magnesium-aluminate spinel were examined after being irradiated with 220 MeV Xe ions. The research aimed to simulate the impact of nuclear fuel fission fragments on the material. The following measurements were taken during the experiments: transmission spectra in the IR region (190-7000) nm, optical absorption spectra in the range (1.2-6.5) eV, and Raman spectra were measured along the depth of ion penetration from the surface to 30 µm. A peak with a broad shape at approximately 5.3 eV can be observed in the optical absorption spectrum of irradiated spinel crystals. This band is linked to the electronic color centers of F+ and F. Meanwhile, the band with a maximum at ~(3-4) eV is attributed to hole color centers. Apart from the typical Raman modes of an unirradiated crystal, additional modes, A1g* (720 cm-1), and Eg* (385 cm-1), manifested mainly as an asymmetric shoulder of the main Eg mode, are also observed. In addition, the Raman spectroscopy method showed that the greatest disordering of crystallinity occurs in the near-surface layer up to 4 μm thick. At the same time, Raman scattering spectroscopy is sensitive to structural changes almost up to the simulated value of the modified layer, which is an excellent express method for certifying the structural properties of crystals modified by swift heavy ions.

Intrinsic emissions and formation of electron-hole trapping centres in excited Li2SO4

Vacuum ultraviolet and thermal activation spectroscopies were used to study the nature of intrinsic emission and the mechanisms of the formation of electron and hole trapping centres in irradiated Li2SO4 powders and crystals. The obtained results along with excitation spectra showed that recombination emission at 3.8–4.2 eV and 4.5–5.5 eV occurs when an electron passes from the second and third sub-bands of the valence band formed from the 2p state of oxygen to the conduction band. It has been determined that Li2SO4 electron and hole trapping centres are created when electrons are trapped in the SO42– anionic sites. The holes are localised in the form of SO4 – radicals. The spectral position and intensity of individual emission bands are dependent on the crystallographic arrangement of localised holes.

Ferromagnetic Interlayer Coupling in CrSBr Crystals Irradiated by Ions.

Layered magnetic materials are becoming a major platform for future spin-based applications. Particularly, the air-stable van der Waals compound CrSBr is attracting considerable interest due to its prominent magneto-transport and magneto-optical properties. In this work, we observe a transition from antiferromagnetic to ferromagnetic behavior in CrSBr crystals exposed to high-energy, non-magnetic ions. Already at moderate fluences, ion irradiation induces a remanent magnetization with hysteresis adapting to the easy-axis anisotropy of the pristine magnetic order up to a critical temperature of 110 K. Structure analysis of the irradiated crystals in conjunction with density functional theory calculations suggests that the displacement of constituent atoms due to collisions with ions and the formation of interstitials favors ferromagnetic order between the layers.

Photoluminescence of high energy xenon ion irradiated magnesium aluminate spinel single crystals

Laser confocal microscopy technique (60 ps laser pulse excitation at 445 nm) and a time-correlated single photon counting (TCSPC) technique have been used to study the photoluminescence (PL) in 152 MeV Xe ion irradiated MgAl2O4 single crystals. It was shown that radiation defects produced by swift xenon ions give rise to broad luminescence band positioned in the 470–800 nm wavelength range. The measurements of the PL decay curves have evidenced that lifetime of defect-related PL signal gradually increases from 6 to 10 ns in 500–620 nm spectral range and decreases with ion fluence increasing. The decrease of the luminescence intensity observed after fluences ∼1013 cm−2 is attributed to overlapping of individual ion track core regions.