Raman and infrared study of 100MeV swift Ag 8+ heavy ion irradiation effects in CaSO 4 ·2H 2 O single crystals

The modifications of calcium sulphate (CaSO 4 ·2H 2 O) single crystals are investigated by means of Raman and Fourier transform infrared spectroscopy (FT-IR) using 100 MeV Ag 8+ ions in the fluence range 1 × 10 11 to 5 × 10 13 ions/cm 2 . It is observed that the intensities of the Raman modes decrease with increase in ion fluence. We determined damage cross-section ( σ ) for all the Raman active modes and found to be different for different Raman modes. Further, FT-IR studies have been carried out to confirm surface amorphisation for a fluence of 1 × 10 13 ions/cm 2 . It is observed that the absorption peaks at 1132–1156 cm −1 corresponds to ν 3 (SO 4 2− ) mode. The decrease in Raman peaks intensity with ion fluence is attributed to degradation of ν 3 (SO 4 2− ) modes present on the surface of the sample

Synthesis and characterization of spherical and rod like nanocrystalline Nd2O3 phosphors

Spherical and rod like nanocrystalline Nd2O3 phosphors have been prepared by solution combustion and hydrothermal methods respectively The Powder X-ray diffraction (PXRD) results confirm that hexagonal A-type Nd2O3 has been obtained with calcination at 900 C for 3 h and the lattice parameters have been evaluated by Rietveld refinement Surface morphology of Nd2O3 phosphors show the formation of nanorods in hydrothermal synthesis whereas spherical particles in combustion method TEM results also confirm the same Raman studies show major peaks which are assigned to F-g and combination of A(g) + E-g modes The PL spectrum shows a series of emission bands at similar to 326-373 nm (UV) 421-485 nm (blue) 529-542 nm (green) and 622 nm (red) The UV blue green and red emission in the PL spectrum indicates that Nd2O3 nanocrystals are promising for high performance materials and white light emitting diodes (LEDs) (C) 2010 Elsevier B V All rights reserve

Swift heavy ion irradiation induced phase transformation in calcite single crystals

Ion irradiation induced phase transformation in calcite single crystals have been studied by means of Raman and infrared spectroscopy using 120 MeV Au 9+ ions. The observed bands have been assigned according to group theory analysis. For higher fluence of 5Ã10 12 ion/cm 2, an extra peak on either side of the 713 cm -1 peak and an increase in the intensity of 1085 cm -1 peak were observed in Raman studies. FTIR spectra exhibit extra absorption bands at 674, 1589 cm -1 and enhancement in bands at 2340 and 2374 cm -1 was observed. This might be due to the phase transformation from calcite to vaterite. The damage cross section (Ï) for all the Raman and FTIR active modes was determined. The increase of FWHM, shift in peak positions and appearance of new peaks indicated that calcite phase is converted into vaterite. © 2009 Elsevier Ltd. All rights reserved

Damage creation in swift heavy ion-irradiated calcite single crystals: Raman and Infrared study

Raman and Infrared studies were carried out on pristine and 100 MeV Ag8+ ion irradiated calcite single crystals in the fluence range 1 à 1011 to 1 à 1013 ions/cm2. Raman and Infrared modes were assigned according to factor theory analysis. It is observed that the intensities of the Raman and infrared bands decrease with increase of ion fluence. The decrease of these bands is attributed to breakage of carbonate ions and other details are discussed. © 2008 Elsevier B.V. All rights reserved

Spectroscopic studies of swift heavy ion irradiated nanophase mullite

Photoluminescence (PL) studies of 100 MeV swift Ag8+ ion bombarded combustion synthesized nanophase mullite has been studied at room temperature (RT) and the results are reported here. A pair of PL bands, one broad band centres at â550 nm and another sharp one at â690 nm are observed with excitation by a 442 nm laser beam. However, when the sample is excited with 326 nm laser beam, three bands with peaks at â¼460, 550 and a well resolved one with peak at 760 nm are observed. It is observed that the PL intensity increases up to 5 à 1011 ions/cm2 and thereafter it decreases with increase of ion fluence. The pristine as well as Ag8+ ion irradiated mullites are characterized by infrared spectroscopy (IR) and X-ray diffraction (XRD) techniques. The decrease in PL intensity is attributed to Al-O and Si-O bonds present as the surface getting amorphized. The effects of Ag8+ irradiation are compared to those obtained with Ni8+ ions and the results are discussed. © 2005 Elsevier B.V. All rights reserved

Synthesis, characterization and photoluminescence properties of Gd 2O3:Eu3 nanophosphors prepared by solution combustion method

Gd2O3:Eu3 (0.58.0 mol) nanophosphors have been prepared by low temperature solution combustion method using metal nitrates as oxidizers and oxalyl dihydrazide (ODH) as a fuel. The phosphors are well characterized by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR) and photoluminescence (PL) techniques. PXRD patterns of as-formed and calcined (800 °C, 3 h) Gd2O3 powders exhibit monoclinic phase with mean crystallite sizes ranging from 20 to 50 nm. Eu3 doping changes the structure from monoclinic to mixed phase of monoclinic and cubic. SEM micrographs shows the products are foamy, agglomerated and fluffy in nature due to the large amount of gases liberated during combustion reaction. Upon 254 nm excitation the photoluminescence of the Gd2O3:Eu 3 particles show red emission at 611 nm corresponding to 5D0â7F2 transition. It is observed that PL intensity increases with calcination temperature. This might be attributed to better crystallization and eliminates the defects, which serve as centers of non-radiative relaxation for nanomaterials. It is observed that the optical energy gap (Eg) is widened with increase Eu3 content. © 2010 Elsevier B.V. All rights reserved

Hydrothermal synthesis of Gd2O3:Eu3+ nanophosphors: Effect of surfactant on structural and luminescence properties

Various morphologies of Eu3+ activated gadolinium oxide have been prepared by hydrothermal method using hexadecylamine (HDA) as surfactant at different experimental conditions. The powder X-ray diffraction studies reveal as-formed product is hexagonal Gd(OH)(3):Eu3+ phase and subsequent heat treatment at 350 and 600 degrees C transforms to monoclinic GdOOH:Eu3+ and cubic Gd2O3:Eu3+ phases respectively. SEM pictures of without surfactant show irregular shaped rods along with flakes. However, in the presence of HDA surfactant, the particles are converted into rods of various sizes. The temperature dependent morphological evolution of Gd2O3:Eu3+ without and with HDA surfactant is studied. TEM micrographs of Gd(OH)(3):Eu3+ sample with HDA confirms smooth nanorods with various diameters in the range 20-100 nm. FTIR studies reveal that HDA surfactant plays an important role in conversion of cubic to hexagonal phases. Among these three phases, cubic phase Gd2O3:Eu3+ (lambda(ex) = 254 nm) show red emission at 612 nm corresponding to D-5(0)-> F-7(2) and is more efficient host than the monoclinic counterpart. The band gap for hexagonal Gd(OH)(3):Eu3+ is more when compared to monoclinic GdOOH:Eu3+ and cubic Gd2O3:Eu3+. (C) 2013 Elsevier B. V. All rights reserved

Effect of Li+-​ion on enhancement of photoluminescence in Gd2O3:Eu3+ nanophosphors prepared by combustion technique

Gd2O3:Eu3+ (4 mol​%) nanophosphor co-​doped with Li+ ions have been synthesized by low-​temp. soln. combustion technique in a short time. Powder X-​ray diffractometer (PXRD)​, SEM, Fourier transform IR spectroscopy (FT-​IR)​, UV-​VIS and photoluminescence (PL) techniques have been employed to characterize the synthesized nanoparticles. It is found that the lattice of Gd2O3:Eu3+ phosphor transforms from monoclinic to cubic as the Li+-​ions are doped. Upon 254 nm excitation, the phosphor showed characteristic luminescence 5D0 → 7FJ (J = 0-​4) of the Eu3+ ions. The electronic transition located at 626 nm (5D0 → 7F2) of Eu3+ ions was stronger than the magnetic dipole transition located at 595 nm (5D0 → 7F1)​. Furthermore, the effects of the Li+ co-​doping as well as calcinations temp. on the PL properties have been studied. The results show that incorporation of Li+ ions in Gd2O3:Eu3+ lattice could induce a remarkable improvement of their PL intensity. The emission intensity was obsd. to be enhanced four times than that of with out Li+-​doped Gd2O3:Eu3+

Ion beam-induced luminescence and photoluminescence of 100 MeV Si8+ ion irradiated kyanite single crystals

Ionoluminescence (IL) of kyanite single crystals during 100 MeV Si8+ ion irradiation has been studied in the fluence range 1.87-7.50Ã1011 ions/cm2. Photoluminescence (PL) of similar dimensional crystals was recorded with same ions and energy in the fluence range 1Ã1011-5Ã1013 ions/cm2 with an excitation of 442 nm He-Cd laser beam. A sharp IL and broad PL peaks at â¼689 and 706 nm were recorded. This is attributed to luminescence centers activated by Fe2+ and Fe3+ ions. It is observed that up to a given fluence, the IL and PL peak intensities increase with increase of Si8+ ion fluence. The stability of the chemical species was studied on with and without irradiated samples by means of FT-IR spectroscopy. The results confirm that the O-Si-H type bonds covering on the surface of the sample. This layer might be acting as a protective layer and thereby reducing the number of non-radiative recombination centers. © 2008 Elsevier Ltd. All rights reserved

Photoluminescence studies of 100 MeV Ni8+ ion irradiated Al2O3 single crystals

We present the results of photoluminescence (PL) measurements on 100 MeV Ni8+ ion irradiated Al2O3 single crystals in the fluence range 1 × 1011 to 5 × 1012 ions/cm2. A sharp PL peaks at ∼693, 695, 707 and 730 nm are recorded with an excitation of 442 nm He–Cd laser beam. The sharp emission peaks at 693 and 695 nm are attributed to R2 and R1 lines of Cr3+ ions, and they are related to the transition from 2Eg → 4A2g. The weaker sharp peaks called N lines appear at ∼707 nm and its origin is ascribed due to closely coupled pairs of Cr3+ ions. The longer wavelength part of the PL spectra at ∼730 nm may be due to increase of groups of more than two Cr3+ ions. It is observed that the broad emission band (450–650 nm) consists of four bands centered at 470, 518, 547 and 618 nm, respectively. The 470, 518 and 547 nm bands are corresponding to F2+, F2 and F22+ defect center, respectively. It is observed that the PL intensity of F2, F22+, R and N lines increases with Ni8+ ion fluence. This can be attributed to increase in concentration of color centers responsible for luminescence through radiative recombination. PACS 61.80.−jh; 61.10.−Nz; 68.37.Ps; 78.66.−