Swift heavy ion induced structural, iono and photoluminescence properties of β-CaSiO₃:Dy³⁺ nanophosphor.
ABSTRACT CaSiO(3):Dy(3+) (1-5 mol%) nanophosphors have been prepared by a low temperature solution combustion method. The structural and luminescence (ionoluminescence; IL and photoluminescence; PL) studies have been carried out for pristine and ion irradiated samples. The XRD patterns of pristine sample show a prominent peak at (320) for the monoclinic structure of β-CaSiO(3). Upon ion irradiation, the intensity of the prominent peak is decreased at the fluence of 7.81 × 10(12)ions cm(-2) and at higher fluence of 15.62 × 10(12)ions cm(-2), the prominent peak completely vanishes. The decrease in peak intensity might be due to the stress induced point defects. On-line IL and in situ PL studies have been carried out on pelletized samples bombarded with 100 MeV Si(7+) ions with fluences in the range (7.81-15.62)×10(12)ions cm(-2). The characteristic emission peaks at 481,574, 664 and 754 nm recorded in both IL and PL are attributed to the luminescence centers activated by Dy(3+) ions. It is found that IL and PL emissions intensity decreases with increase in Si(7+) ion fluence. The decrease in intensity can be due to the destruction of Si-O-Si and O-Si-O type species present on the surface of the sample. FTIR studies also confirm the Si-O-Si and O-Si-O type species observed to be sensitive for swift heavy ion (SHI) irradiated samples.
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ABSTRACT: A near-ultra violet (UV) converted LiMgBO3:Dy3+ nanophosphors have been synthesized by the combustion method. The structural, spectral and optical properties were examined by powder X-ray diffraction, fluorescent spectrophotometry and UV–vis spectroscopy. The excitation spectra of the phosphors contain sharp peaks at 294, 323, 348 and 385 nm due to the 4f–4f transition of the Dy3+ ion. The phosphor is effi-ciently excited by near-UV chips. Upon near-UV excitation the phosphor emits intense blue and yellow with a weak red band centered at 484, 573 and 669 nm respectively, ascribed to the transition of Dy3+ ion from 4F9/2→6H15/2, 6H13/2, 6H11/2. The diffuse reflectance spectra of the phosphors were consistent with the excitation spectra and were used to calculate the band gap of the material, approximated to be 5.4 eV. The calculated CIE coordinates (0.45, 0.46) under 348 nm excitation were found to be in the white spectrum region. For surface investigation, X-ray photoelectron spectroscopy was used which confirms the presence of all the elements on the surface of the material.Applied Surface Science 02/2015; 329:40-46. DOI:10.1016/j.apsusc.2014.12.056 · 2.54 Impact Factor
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ABSTRACT: A series of new phosphors of BaCa2Si3O9:Ln3+, (Ln = Eu, Ce, Dy, Sm, Tb) were synthesized by precipitation based method. Good crystallinity was achieved after annealing the sample at 750 °C for 1 h in air. X-ray powder diffraction (XRD) result confirmed the formation of desired BaCa2Si3O9 host. The photoluminescent excitation and emission properties of Ln3+, (Ln = Eu, Ce, Dy, Sm, Tb) activated BaCa2Si3O9 were investigated in detail. The photoluminescence (PL) analysis of individual Ln3+, (Ln = Eu, Ce, Dy, Sm, Tb) activated BaCa2Si3O9 phosphors exhibits interesting characteristic emission properties in their respective regions. From the measured emission spectra, Judd–Ofelt (J–O) intensity parameters (Ω2, Ω4, Ω6) have been calculated and using these J–O parameters various radiative parameters such as radiative transition probabilities (Arad), radiative lifetimes (τR), branching ratios (βR) and relative quantum yield have been calculated for the studied ions.Materials Chemistry and Physics 10/2014; 147(3):594–603. DOI:10.1016/j.matchemphys.2014.05.035 · 2.13 Impact Factor
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ABSTRACT: The effect of 120 MeVAg9? ion irradiation on the structural, optical and luminescence properties of NaSr1-xBO3:xDy3? (x = 0.5–2.5 mol%) phosphor synthesized by the conventional solid state reaction route is reported. The samples were irradiated with Ag9? swift heavy ions (SHIs) using fluences of 1 9 1012, 5 9 1012 and 1 9 1013 ions cm-2. The unirradiated as well as irradiated samples were characterized by powder X-ray diffraction (PXRD), diffuse reflectance (DR) and photoluminescence techniques. PXRD confirms no change in the phase after irradiation except that loss of crystallinity had been observed which may be due to the fragmentation caused by the SHI. A blue shift in the absorption band of the DR was observed, resulting in an increase in the band gap from 5.61 eV to 5.77 eV, after ion irradiation. An increase in photoluminescence intensity (excited at 385 nm) was observed with increased ion fluences. The ratio of the blue to yellow emission peaks (I483/I577) was calculated and found to be varying with ion fluences suggesting that the white light can be achieved by tailoring this yellow to blue ratio. The Commission Internationale de l’Eclairage coordinates were calculated and found to move toward the white region after irradiation.Journal of Materials Science 06/2014; DOI:10.1007/s10853-014-8367-0 · 2.31 Impact Factor