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Abstract: Nanoparticles of Eu3+ doped Mg2SiO4 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 3h. The Powder X-ray diffraction (PXRD) patterns of the sample reveled orthorhombic structure with α-phase. The crystallite size using Scherer''s formula is found to be in the range 50–60nm. The effect of Eu3+ on the luminescence characteristics of Mg2SiO4 is studied and the results are presented here. These phosphors exhibit bright red color upon excitation by 256nm light and showed the characteristic emission of the Eu3+ ions. The electronic transition corresponding to 5D0 → 7F2 of Eu3+ ions (612nm) is stronger than the magnetic dipole transition corresponding to 5D0 → 7F1 of Eu3+ ions (590nm). Thermoluminescence (TL) characteristics of γ-rayed Mg2SiO4:Eu3+ phosphors are studied. Two prominent and well-resolved TL glows with peaks at 202°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. [Copyright &y& Elsevier]

Abstract: Calcium fluoride nanocrystals (CaF2) were synthesized by two different techniques namely co-precipitation and hydrothermal. The synthesized nanocrystals were characterized by powder X-ray diffraction (PXRD), Fourier transform infrared red spectroscopy (FTIR), scanning electron microscopy (SEM), optical absorption and photoluminescence (PL). The crystallite size estimated using Scherer''s formula was found to be in the range 30–35nm for nanocrystals synthesized by co-precipitation method where as in case of hydrothermally synthesized nanocrystals it is in the range 20–28nm which is less compared to those obtained by co-precipitation method. The morphological features as studied using SEM revealed that the nanocrystals are agglomerated, crispy with porous. The SEM images of hydrothermally synthesized nanocrystals showed less agglomeration than those obtained by co-precipitation method and the images confirm the formation of nanoparticles. The optical absorption spectrum showed a strong absorption band peaked at 244nm for nanocrystals synthesized by co-precipitation method and it is 218nm peak in case of hydrothermally synthesized ones. The PL emission spectrum showed two prominent emission bands peaked at 330 and 600nm when excited at 218nm. [Copyright &y& Elsevier]

Abstract: The modifications of calcium sulphate (CaSO4·2H2O) single crystals are investigated by means of Raman and Fourier transform infrared spectroscopy (FT-IR) using 100MeV Ag8+ ions in the fluence range 1×1011 to 5×1013 ions/cm2. 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 1×1013 ions/cm2. It is observed that the absorption peaks at 1132–1156cm−1 corresponds to ν 3(SO4 2−) mode. The decrease in Raman peaks intensity with ion fluence is attributed to degradation of ν 3(SO4 2−) modes present on the surface of the sample. [Copyright &y& Elsevier]