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Phosphor Photoluminescence Thermoluminescence Optical absorption a b s t r a c t Nanoparticles of Eu 3+ doped Mg 2 SiO 4 are prepared using low temperature solution combustion technique with metal nitrate as precursor and urea as fuel. The synthesized samples are calcined at 800• C for 3 h. The Powder X-ray diffraction (PXRD) patterns of the sample reveled orthorhombic structure with ␣-phase. The crystallite size using Scherer's formula is found to be in the range 50-60 nm. • C and 345• C besides a shoulder with peak at ∼240• C are observed. The trapping parameters-activation energy (E), order of kinetics (b) and frequency factor (s) are calculated using glow curve shape method and the results obtained are discussed.

Nanocrystalline Y 2 O 3 is synthesized by solution combustion technique using urea and glycine as fuels. X-ray diffraction (XRD) pattern of as prepared sample shows amorphous nature while annealed samples show cubic nature. The average crystallite size is calculated using Scherrer's formula and is found to be in the range 14-30 nm for samples synthesized using urea and 15-20 nm for samples synthesized using glycine respectively. Field emission scanning electron microscopy (FE-SEM) image of 1173 K annealed Y 2 O 3 samples show well separated spherical shape particles and the average particle size is found to be in the range 28-35 nm. Fourier transformed infrared (FTIR) and Raman spectroscopy reveals a stretching of Y-O bond. Electron spin resonance (ESR) shows V − center, O 2 − and Y 2+ defects. A broad photoluminescence (PL) emission with peak at~386 nm is observed when the sample is excited with 252 nm. Thermoluminescence (TL) properties of γ-irradiated Y 2 O 3 nanopowder are studied at a heating rate of 5 K s −1 . The samples prepared by using urea show a prominent and well resolved peak at~383 K and a weak one at~570 K. It is also found that TL glow peak intensity (I m1 ) at~383 K increases with increase in γ-dose up to~6.0 kGy and then decreases with increase in dose. However, glycine used Y 2 O 3 shows a prominent TL glow with peaks at 396 K and 590 K. Among the fuels, urea used Y 2 O 3 shows simple and well resolved TL glows. This might be due to fuel and hence particle size effect. The kinetic parameters are calculated by Chen's glow curve peak shape method and results are discussed in detail.

Pure yttrium oxide (Y 2 O 3 ) was prepared by solution combustion technique using disodium ethylene diamine tetra acetic acid (EDTA-Na 2 ) as fuel at~350°C. Powder X-ray diffraction (PXRD) pattern of Y 2 O 3 revealed cubic crystalline structure with crystallite size in the range of 18-23 nm. The scanning electron microscopy (SEM) indicated the foamy and fluffy nature of the sample. Fourier transformed infrared spectroscopy (FTIR) revealed four prominent absorption with peaks at 3395, 1433, 875 and 566 cm − 1 . From the optical absorption studies the energy gap of the synthesized sample was found to be 5.72 eV. Two well resolved thermoluminescence (TL) glows with peaks at 475 and 626 K were observed in γ-irradiated Y 2 O 3 . The glow curves were analyzed and the average activation energy was found to be 0.505 and 0.977 eV respectively.

a b s t r a c tLuminescence exhibiting europium doped yttrium oxide (Y 2 O 3 :Eu 3+ ) phosphor was prepared by solution combustion method, using disodium ethylene diamine tetra acetic acid (EDTA-Na 2 ) as fuel at ∼350 • C. Powder X-ray diffraction (PXRD) pattern of Y 2 O 3 :Eu 3+ revealed the cubic crystalline phase. The morphology of the samples was studied by scanning electron microscopy (SEM) and was foamy, fluffy and porous in nature. Fourier transformed infrared spectroscopy (FTIR) revealed prominent absorption with peaks at 3415, 1435, 875 and 565 cm −1 . Optical absorption studies showed the energy gap of the synthesized samples to be 5.4-5.5 eV. The photoluminescence (PL) of Y 2 O 3 :Eu 3+ exhibiting emission peak at 611 nm under the excitation of 254 nm. Thermoluminescence of ␥-irradiated Y 2 O 3 :Eu 3+ showed two well resolved TL glows with peaks at 460 and 610 K and they were analyzed by glow curve shape method and the activation energies were found to be 0.421 eV and 1.016 eV respectively.

Calcium fluoride (CaF 2 ) nanoparticles were synthesized by co-precipitation method and characterized by powder X-ray diffraction (PXRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM). Also, optical absorption (OA) and photoluminescence (PL) studies on gamma irradiated (γ-rayed) CaF 2 nanoparticles were carried out. The XRD patterns confirmed the cubic crystallinity of the samples and the particle size was found to be ~25 nm. The purity of the synthesized nanoparticles was confirmed by FTIR spectrum. The morphological features studied using SEM revealed the agglomerated and porous nature of nanoparticles. γ-rayed CaF 2 nanoparticles showed a prominent absorption with a peak at ~360 nm besides three weak but well separated absorptions at ~ 267, 442 and 510 nm. The various defect centers responsible for the absorption peaks were identified. The PL studies of samples showed strong emissions at ~396 nm and 425 nm. The observed PL emissions are attributed to defects created in nanocrystalline CaF 2 .Citation: Pandurangappa C, Lakshminarasappa BN (2011) Optical absorption and Photoluminescence studies in Gamma-irradiated nanocrystalline CaF 2 .

Thermoluminescence (TL) of combustion-synthesized aluminum oxide bombarded with 120 MeV swift Au 9+ ions in the fluence range of 1 × 10 11 − 2 × 10 13 ions cm −2 has been studied at room temperature. Two TL glows-a well-resolved one with peak at ∼623 K (Tg 2 ) and another unresolved one at ∼513 K (Tg1)-are recorded at a heating rate of 10 K s −1 . It is found that the TL intensity increases with the fluence up to 1 × 10 13 ions cm −2 and then decreases with increase in fluence. Also, the prominent glow peak temperature (Tg 2 ) is found to be shifted towards the lower temperature region, while the TL intensity increases with the increase in ion fluence. In the case of heat-treated samples, the TL intensity is observed to be enhanced further. However, in the case of samples heat-treated beyond 973 K, the TL intensity is found to be decreased with the increase in heat treatment. The glow curves are analyzed by the glow curve deconvolution technique and trap parameters are estimated and discussed in this paper.

a b s t r a c tNanoparticles of pure yttrium oxide (Y 2 O 3 ) have been prepared by sol gel method. The powder X-ray diffraction (PXRD) pattern of as synthesized sample showed the amorphous nature. The as synthesized Y 2 O 3 powders are annealed at 500, 600, 700, 800 and 900°C for 2 h. Y 2 O 3 powder heat treated for 600°C showed cubic phase and the crystallite sizes are found to be $13 nm. Fourier transformed infrared spectroscopy (FTIR) revealed absorption with peaks at 3434, 1724, 1525, 1400, 847, 562 and 465 cm À1 . Photoluminescence (PL) of 100 MeV Si 8+ ion irradiated samples shows emission with peaks at 417, 432, 465 nm. It is found that PL intensity increases with increasing in ion fluence up to $3 Â 10 12 ions cm À2 and then decreases with further increase in ion fluence. A well resolved thermoluminescence (TL) glow with peak at $430 K (Tm 1 ) and an unresolved TL glow with peak at $538 (Tm 2 ), 584 K (Tm 3 ) are observed in ion irradiated samples.