[en] Thermoluminescence (TL) of natural kyanite single crystals bombarded with 100 MeV Si⁺⁸ ions with fluences in the range 1x10¹¹-5x10¹³ ions/cm² has been studied at room temperature (RT). Two TL glows, a medium one at ∼445 K and another intense one at ∼550 K are recorded in single crystals of kyanite. However, in the case of pelletized samples, similar TL glows but with peaks at ∼475 and 615 K, respectively, are recorded at a warming rate of 20 K/min. It is found that as the fluence of Si⁺⁸ ion increases, the TL intensity increases. It is also found that the characteristic TL glow peaks appear at higher temperature side in pelletized kyanite than those in crystalline ones, however, the glow peak temperatures remain steady in a given system irrespective of the ion dose. The enhancement in TL intensity and shifting of TL glow peaks to higher temperature side in pelletized kyanite samples are attributed to the particle nature of the phosphor and/or pressure-induced defects in the phosphor

[en] Photoluminescence (PL) of pelletized mullite samples irradiated with 100 MeV swift Ni⁸⁺ ions with fluences in the range 1 x 10¹¹-5 x 10¹³ ions/cm² have been studied at RT. A broad and strong PL emission band with peak at ∼537 nm besides a sharp emission band with peak at ∼705 nm have been recorded in combustion synthesized mullite. However, a single broad emission with peak at ∼537 nm have been recorded in mullite synthesized by sol-gel technique at an excitation of 442 nm laser beam. It is found that PL intensity is decreases with increase of Ni⁸⁺ ion fluence. The decrease in PL intensity is attributed to destruction of Al-O and Si-O bonds in the samples. Infrared absorption (IR) studies of as it is and Ni⁸⁺ ion irradiated mullites have also been studied and results obtained are discussed

[en] Ionoluminescence (IL) and photoluminescence (PL) of aluminum silicates irradiated with 100 MeV swift Ni⁺⁸ ions with fluences in the range 7.5x10¹⁰-1.0x10¹⁴ ions/cm² have been studied. A pair of IL bands with peaks at ∼775 and 875 nm are recorded in both natural crystalline and pelletized kyanite samples. And, a pair of sharp as well as strong PL emission bands with peaks at ∼688.7 and 705.9 nm along with a broad emission band in the region 710-900 nm are recorded in these samples with an excitation of 442 nm laser beam. It is found that both IL and PL intensities decrease with increase of ion fluence. The decrease of IL is attributed to amorphization of the material

[en] Thermoluminescence (TL) of as it is and heat treated gaodati single crystals bombarded with 100 MeV Ag⁺⁸ in the dose range l x 10¹¹- 7.5x1x10¹¹ ions/cm² have been studied at room temperature. A single and well resolved glow peak at ∼530K is observed in all the samples. It is observed that the TL intensity is less in ion irradiated samples when compared to gamma irradiated samples. The characterization of as it is and ion irradiated are studied using Raman studies and Infrared spectroscopy. The Raman studies indicate the characteristic mode v₁(SO₄) at 1008 cm^-1 is present in all the samples. It is observed that the intensity of v₁(SO₄) mode increases up to 5x10¹¹ ions/cm² and there after it decreases. In case of heat treated samples, the v₁(SO₄) mode decrease up to 400 deg C and there after it increases. The decrease in intensity of v₁(SO₄) mode with increase of ion fluence is attributed to amorphisation of material. The increase in v₁(SO₄) mode above 400 deg C might be to structural changes from gypsum to bassanite. (author)

[en] Photoluminescence (PL) and thermoluminescence (TL) of laboratory synthesized g-irradiated aluminum silicates have been studied at RT. Two sharp PL emission bands with peaks around 740 and 763nm have been observed in solution combustion synthesized g-rayed mullite (I) excited with 400 nm light. A pair of sharp emission bands with peaks at 695 and 748 nm are observed in sol-gel synthesized g-rayed mullite (II) excited with 411 nm light. It is found that the PL intensity is enhanced in sol-gel synthesized mullite when compared to that in solution synthesized combustion mullite as well as in natural kyanite and it is attributed to particle nature of the phosphor. Thermoluminescence studies of the above samples g-irradiated for 8.663 x 10³Gy at RT indicates a weak glow with peak at ∼125 deg C was observed in all these samples. However, a second and strong glow with peak at ∼250 deg C is observed only in mullite (I) and kyanites. It is found that TL intensity is higher in solution combustion synthesized mullite when compared to that in sol-gel and natural kyanite. (author)

[en] Mimosa pudica(MP) plant extract was used to prepare Y₂O₃:Tm³⁺ (1-11mol %) nanoscale superstructure with nitrate source as precursors. The samples were characterized by advanced characterization techniques. The PXRD peaks indicates crystalline, no impurity peaks were present with body centre cubic structure of Y₂O₃. Photoluminescence emission spectra shows blue color emission at 358 nm excitation wavelength. The major peak of Tm³⁺ was at 453 nm and two very weak peaks were observed at ∼ 474 nm attributed to the transitions of ¹D₂ → ³ F₄ and ¹G₄ → ³H₆, res. The calculated color co-ordinates were matches to the NTSC blue color. Correlated color temperature was ∼ 4000 K. So the Y₂O₃:Tm³⁺ nanophosphor could be used for blue component in the warm WLED and SSL devices. (paper)

[en] Well-crystallized tetragonal layered BiOBr and Bi_0_._9_5Sm_0_._0_5OBr phosphors were prepared by the solid state method. These compounds were characterized using powder X-Ray diffraction and photoluminescence technique. In PL spectra, the electric dipole transitions dominate than other transitions which indicate that the Sm"3"+ ions occupy a site with an inversion center of BiOBr. CIE chromaticity diagram confirmed that these phosphors can be useful in the fabrication of red component in white light emitting diodes (WLEDs) for display device applications.

[en] For the first time Pr³⁺ (1-11 mol %) doped Y₂O₃nanophosphors were synthesized by ultrasound supported sonochemical method using mimosa pudica (MP) leaves extract as bio-surfactant. The obtained product was heat treated at 700°C for 3 h and used for characterization. The powder X-ray diffraction (PXRD) profiles of nanophosphors showed cubic phase structure. The sonication time and concentration of bio-surfactant play a vital role in tuning the morphologies of Y₂O₃. The particle size was further confirmed by transmission electron microscope (TEM) and it was found to be in the range of 20-30 nm. The band gap energy of the phosphors were estimated by making use of diffuse reflectance spectrum (DRS) and the values were found to be in the range of 5.67 – 5.80 eV. Under 447 nm excitation wavelength, the photoluminescence (PL) emission spectrum was recorded. The PL emission spectra consist of sharp peaks centred at 554, 612 and 738 nm and were attributed to ³P₀→³H₅, ³P₀→³H₆, and ³P₀→³F₄ transitions respectively. The 5 mol% Pr³⁺ doped Y₂O₃nanophosphors showed maximum intensity. Further CIE and CCT were estimated and found that the color coordinates lies in between (0.593, 0.412) and (0.358, 0.544) respectively. Results obtained evident that the phosphor was highly useful in display device applications. (paper)

[en] The undoped and Ce³⁺ doped (1-9 mol %) CdSiO₃ powder was successfully prepared via low temperature solution combustion method for the first time using oxalyl dihydrizide (ODH) as a fuel. The prepared powder was characterized by powder X-ray diffraction (PXRD), Fourier Transform Infra-Red (FTIR), Thermo gravimetric and Differential Thermo gravimetric (TG/DTA) and scanning electron microscopy (SEM). The PXRD results measurement indicated that the powder calcined at 800 deg C for 2 hr had a good crystallization monoclinic phase. The calcination temperature for the formation of monoclinic CdSiO₃ powder was found to be very low as compared to that of powder prepared by solid-state and sol-gel method. The effect of calcination temperature on phase formation was also investigated using PXRD, TG/DTA and FTIR spectra. The microstructure of CdSiO₃ powder was studied by scanning electronic microscope (SEM), which indicates that the powder is highly porous and microcrystalline in nature. The thermoluminescence of CdSiO₃:Ce³⁺ nanopowder exposed to UV irradiation exhibited one main peak centered at 175 deg C. The intensity of the main peak increases up to 30 min UV irradiation then it decreases with further increase of UV irradiation dose. The trap parameters are analysed using glow curve deconvolution and peak shape method and results are discussed in detail. (author)

[en] Ionoluminescence (IL) of kyanite single crystals bombarded with 100 MeV swift Ag⁸⁺ ions with fluences in the range 1.87-7.5x10¹¹ ions/cm² has been studied. A pair of sharp IL peaks at ∼689 and 706 nm along with broad emission in the region 710-800 nm are recorded in both crystalline and pelletized samples. Similar results are recorded in Photoluminescence (PL) of pelletized kyanite bombarded with same ions and energy with fluences in the range 1x10¹¹-5x10¹³ ions/cm² with an excitation of 442 nm laser beam. The characteristic pair of sharp emission peaks at 689 and 706 nm in both IL and PL is attributed to luminescence centers activated by Fe²⁺ and Fe³⁺ ions. The reduction in IL and PL bands intensity with increase of ion fluence might be attributed to degradation of Si-O (2ν₃) bonds, present on the surface of the sample