100MeV Si8+ Ion Induced Luminescence and Thermoluminescence of Nanocrystalline Mg2SiO4:Eu3+

Nanoparticles of Mg2SiO4:Eu3+ have been prepared by the solution combustion technique and the grain size estimated by PXRD is found to be in the range 40-50 nm. Ionoluminescence (IL) studies of Mg2SiO4:Eu3+ pellets bombarded with 100 MeV Si8+ ions with fluences in the range 1.124-22.48×1012 ions cm−2 are carried out at IUAC, New Delhi, India. Five prominent IL bands with peaks at 580 nm, 590 nm, 612 nm, 655 nm and 705 nm are recorded. These characteristic emissions are attributed to the luminescence centers activated by Eu3+ cations. It is found that IL intensity decreases rapidly in the beginning. Later on, the intensity decreases slowly with further increase of ion fluence. The reduction in the ionoluminescence intensity with increase of ion fluence might be attributed to degradation of Si-O (ν3) and Si-O (2ν3) bonds present on the surface of the sample. The red emission with peak at 612 nm is due to characteristic emission of 5D0→7F2 of the Eu3+ cations. Thermoluminescence (TL) studies of Mg2SiO4:Eu3+ pellets bombarded with 100 MeV Si8+ cations with fluences in the range 5×1011 ions cm−2 to 5×1013 ions cm−2 are made at RT. Two prominent and well resolved TL glows with peaks at ∼220 °C and ∼370 °C are observed. It is observed that TL intensity increases with increase of ion fluence. This might be due to creation of new traps during swift heavy ion irradiation.

Effect of 100 MeV swift Si8+ ions on structural and thermoluminescence properties of Y2O3:Dy3+nanophosphor

Nanoparticles of Y2O3:Dy3+ were prepared by the solution combustion method. The X-ray diffraction pattern of the 900°C annealed sample shows a cubic structure and the average crystallite size was found to be 31.49 nm. The field emission scanning electron microscopy image of the 900°C annealed sample shows well-separated spherical shape particles and the average particle size is found to be in a range 40 nm. Pellets of Y2O3:Dy3+ were irradiated with 100 MeV swift Si8+ ions for the fluence range of 3 × 1011_3 × 1013 ions cm−2. Pristine Y2O3:Dy3+ shows seven Raman modes with peaks at 129, 160, 330, 376, 434, 467 and 590 cm−1. The intensity of these modes decreases with an increase in ion fluence. A well-resolved thermoluminescence glow with peaks at ∼414 K (Tm1) and ∼614 K (Tm2) were observed in Si8+ ion-irradiated samples. It is found that glow peak intensity at 414 K increases with an increase in the dopant concentration up to 0.6 mol% and then decreases with an increase in dopant concentration. The high-temperature glow peak (614 K) intensity linearly increases with an increase in ion fluence. The broad TL glow curves were deconvoluted using the glow curve deconvoluted method and kinetic parameters were calculated using the general order kinetic equation

Optical absorption and thermoluminescence studies in 100MeV swift heavy ion irradiated CaF 2 crystals

Pure and Ytterbium (Yb) doped Calcium fluoride (CaF2) single crystals were irradiated with 100 MeV Ni7+ ions for fluences in the range 5 × 1011–2.5 × 1013 ions cm−2. The irradiated crystals were characterized by Optical absorption (OA) and Thermoluminescence (TL) techniques. The OA spectra of ion irradiated pure CaF2 crystals showed a broad absorption with peak at ∼556 nm and a weak one at ∼220 nm, whereas the Yb doped crystals showed two strong absorption bands at ∼300 and 550 nm. From the study of OA spectra, the defect centers responsible for the absorption were identified. TL measurements of Ni7+ ion irradiated pure CaF2 samples indicated a strong TL glow with peak at ∼510 K. However, the Yb doped crystals showed two TL glows at ∼406 and 496 K. The OA and TL intensity were found to increase with increase of ion fluence upto 1 × 1013 ions cm−2 and thereafter it decreased with further increase of fluence. The results obtained are discussed in detail

Thermoluminescence Studies of γ-Irradiated Nanocrystalline Y3Al5O12

Nanocrystalline yttrium aluminum garnet (Y3Al5O12) is synthesized by combustion technique. The X-ray diffraction (XRD) pattern of 900 °C annealed sample revealed a cubic structure. The average crystallite size is found to be 20.5 nm. γ-irradiated Y3Al5O12 exhibits two thermoluminescence (TL) glows: a prominent one with a peak at ∼410 K and another one with a peak at ∼575 K. It is found that the TL glow peak intensity at 410 K increases, while its glow peak temperature is almost steady with an increase in the γ-dose. The effect of the heating rate on the TL glow curve is studied. It is found that Tm1 shifts towards higher temperature region while the Im1 decreases with an increase in the heating rate. The TL glow curves are analyzed by Chen's peak shape method and the TL parameters are estimated

Ion Beam Induced Cubic To Monoclinic Phase Transformation of Nanocrystalline Yttria

Sol gel derived nanocrystalline yttria pellets are irradiated with 120 MeV Ag9+ ions for fluence in the range 1 � 1012–3 � 1013 ions cm2 . Pristine and irradiated samples are characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and Raman spectroscopy. XRD pattern of pristine Y2O3 nanocrystal reveal cubic structure. A new XRD peak at 30.36� is observed in pellet irradiated with 1 � 1013 ions cm2 . The peak at 30.36� is corresponding to ð4 0 � 2Þ plane of monoclinic phase. The diffraction intensity of ð4 0 � 2Þ plane increases with Ag9+ ion fluence. Raman spectrum of pristine pellet show bands corresponding to cubic phase. And, ion irradiated sample show new peaks at 410, 514 and 641 cm1 corresponding monoclinic phase. HR-TEM and SAED pattern of ion irradiated sample confirmed the presence of monoclinic phase. Hence, it is confirmed that, 120 MeV Ag9+ ions induce phase transformation in nanocrystalline Y2O3

H-1 NMR study of internal motions and quantum rotational tunneling in (CH3)(4)NGeCl3

(CH3)(4)NGeCl3 is prepared, characterized and studied using H-1 NMR spin lattice relaxation time and second moment to understand the internal motions and quantum rotational tunneling. Proton second moment is measured at 7 MHz as function of temperature in the range 300-77 K and spin lattice relaxation time (T-1) is measured at two Larmor frequencies, as a function of temperature in the range 270-17 K employing a homemade wide-line/pulsed NMR spectrometers. T-1 data are analyzed in two temperature regions using relevant theoretical models. The relaxation in the higher temperatures (270-115 K) is attributed to the hindered reorientations of symmetric groups (CH3 and (CH3)(4)N). Broad asymmetric T-1 minima observed below 115 K down to 17 K are attributed to quantum rotational tunneling of the inequivalent methyl groups. Copyright (c) 2007 John Wiley & Sons, Ltd

Modification of optical and electrical properties of zinc oxide-coated porous silicon nanostructures induced by swift heavy ion

Morphological and optical characteristics of radio frequency-sputtered zinc aluminum oxide over porous silicon (PS) substrates were studied before and after irradiating composite films with 130 MeV of nickel ions at different fluences varying from 1 × 10(12) to 3 × 10(13) ions/cm(2). The effect of irradiation on the composite structure was investigated by scanning electron microscopy, X-ray diffraction (XRD), photoluminescence (PL), and cathodoluminescence spectroscopy. Current–voltage characteristics of ZnO-PS heterojunctions were also measured. As compared to the granular crystallites of zinc oxide layer, Al-doped zinc oxide (ZnO) layer showed a flaky structure. The PL spectrum of the pristine composite structure consists of the emission from the ZnO layer as well as the near-infrared emission from the PS substrate. Due to an increase in the number of deep-level defects, possibly oxygen vacancies after swift ion irradiation, PS-Al-doped ZnO nanocomposites formed with high-porosity PS are shown to demonstrate a broadening in the PL emission band, leading to the white light emission. The broadening effect is found to increase with an increase in the ion fluence and porosity. XRD study revealed the relative resistance of the film against the irradiation, i.e., the irradiation of the structure failed to completely amorphize the structure, suggesting its possible application in optoelectronics and sensing applications under harsh radiation conditions