Ritesh Palaspagar - Academia.edu (original) (raw)
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Papers by Ritesh Palaspagar
Macromolecular Symposia, 2019
The polycrystalline powder sample of Bi 3+-activated strontium yttrium borate phosphor Sr 3 Y 1−x... more The polycrystalline powder sample of Bi 3+-activated strontium yttrium borate phosphor Sr 3 Y 1−x (BO 3) 3 : x Bi 3+ (x = 3, 4, 5 mole%) is prepared by solution combustion technique. Formation of phosphor in the desired crystalline phase is confirmed by powder X-ray diffraction characterization and FTIR, SEM images of the synthesized phosphor show the irregular grains with average particle size 2.5 µm. Luminescence properties of the synthesized phosphor are investigated at room temperature. The excitation spectrum consists of a single broad absorption band from 200 to 370 nm with the prominent excitation peak at 336 nm [ 1 S 0 to 3 P 1 of Bi 3+ ions] and weak excitation peak at 254 nm [ 1 S 0 to 1 P 1 of Bi 3+ ions]. Strongest emission peak of 492 nm wavelength that is of blue light is observed at 336 nm UV light excitation. Sr 3 Y 1−x (BO 3) 3 : x Bi 3+ phosphor emits blue light. As Bi 3+ is sensitive to the surrounding crystal field environment it shows weak excitation peak at 254 nm, which gives emission at 413 nm. Hence, Sr 3 Y 1−x (BO 3) 3 : x Bi 3+ is new UV excited blue emitting phosphor useful for UV/blue chip WLEDs.
ABSTRACT In the present work we report the preparation and photoluminescence characteristics of D... more ABSTRACT In the present work we report the preparation and photoluminescence characteristics of Dy3+ doped borate phosphor K2Al2B2O7:Dy3+. The fine polycrystalline powder samples of K2Al2B2O7:Dy3+ has been prepared by a novel combustion technique. This method is based on the exothermic redox reaction involves, metal nitrates and organic fuel (urea). The formation of samples was confirmed by powder XRD technique. The photoluminescence properties of borate phosphors have been investigated on fluorescence spectrometer (F-7000). The PL excitation spectra of K2Al2B2O7:Dy3+ consists of several bands peaking at 241 nm, 297 nm, 324 nm, 350 nm, 364 nm and 387 nm. Since the prominent excitation peaks are above 360nm, the phosphor may useful for solid state lighting application. The emission spectrum monitored at 351 nm excitation consists of blue emission band peaking at 481 nm and yellow emission band peaking at 574nm.
Journal of Luminescence, 2013
A combustion synthesis method has been developed for synthesis of Eu 2+ doped CaAlSiN3 phosphor a... more A combustion synthesis method has been developed for synthesis of Eu 2+ doped CaAlSiN3 phosphor and its photoluminescence properties were investigated. Ca, Al, Si, and Eu2O3 powders were used as the Ca, Al, Si and Eu sources. The addition of NaN3, NH4Cl and Si3N4 powders was found to increase significantly the product yield. These powders were mixed and pressed into a compact, which was then wrapped up with an igniting agent (i.e., Mg+Fe3O4). The compact was ignited by electrical heating under a N2 pressure of ≤1.0 MPa. Effects of these experimental parameters on the product yield were investigated and a reaction mechanism was proposed. The synthesized CaAlSiN3:Eu 2+ phosphor absorbs light in the region of 200-600 nm and shows a broad band emission in the region of 500-800 nm due to the 4f 6 5d 1 → 4f 7 transition of Eu 2+. The sample doped with Eu 2+ at the optimized molar ratio of 0.04 is efficiently excited by the blue light (460 nm) and generates emission peaking at ~650 nm with peak emission intensity ~106% of a commercially available phosphor, YAG:Ce 3+ (P46-Y3).The internal quantum efficiency of the synthesized phosphor was measured to be 71%, compared to 69% of the YAG:Ce 3+ (P46-Y3).
Journal of Alloys and Compounds, 2014
Optically efficient terbium activated alkaline earth metal tungstate nano phosphors (AWO 4 [A = C... more Optically efficient terbium activated alkaline earth metal tungstate nano phosphors (AWO 4 [A = Ca, Sr]) with different doping concentrations have been prepared by mechanochemically assisted solid state metathesis reaction at room temperature for the first time. The prepared phosphors were characterized by the X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscope (SEM), Fourier transform Raman (FT-Raman) spectroscopy, photoluminescence and diffuse reflectance spectroscopy measurements. The XRD and Raman spectra results showed that the prepared powders present a scheelite-type tetragonal structure. FTIR spectra exhibited a high absorption band situated at around 850 cm-1 , which was ascribed to the W-O antisymmetric stretching vibrations into the [WO 4 ] 2tetrahedron groups and the SEM images reveal that the particle sizes were in the range of 20-60 nm. The excitation and the emission spectra were measured to characterize the luminescent properties of the phosphors. The excitation spectrum exhibits a charge transfer broad band along with some sharp peaks from the typical 4f-4f transitions of Tb 3?. Under excitation of UV light, these AWO 4 :xTb 3? (A = Ca, Sr) phosphors showed a strong emission band centered at 545 nm (green) which corresponds to 5 D 4 ? 7 F 5 transition of Tb 3?. Analysis of the emission spectra with different Tb 3? concentrations revealed that the optimum dopant concentration for CaWO 4 :xTb 3? and SrWO 4 :xTb 3? phosphors are about 8 and 6 mol% of Tb 3?. The green emission intensity of the solid state meta-thesis prepared CaWO 4 :0.08Tb 3? and SrWO 4 :0.06Tb 3? phosphors are 1.5 and 1.2 times greater than that of the commercial LaPO 4 :Ce, Tb green phosphor. All properties show that AWO 4 :Tb 3? (A = Ca, Sr) is a very appropriate green-emitting phosphor for fluorescent lamp applications.
Optik, 2015
Abstract This paper reports reduction of Eu 3+ → Eu 2+ in BaAl 2 B 2 O 7 host prepared in an oxi... more Abstract This paper reports reduction of Eu 3+ → Eu 2+ in BaAl 2 B 2 O 7 host prepared in an oxidizing environment by modified solution combustion synthesis technique. The crystal phase and surface morphology of the prepared phosphor have been studied by powder X-ray diffraction (XRD) and FE-SEM images, respectively. Photoluminescence emission spectra of BaAl 2 B 2 O 7 :Eu 2+ exhibits a strong emission band peaking at 375 nm (UV-A region), upon excited by 309 nm near UV light. For lower concentrations of Eu 2+ , the emission intensity of BaAl 2 B 2 O 7 :Eu 2+ was measured. This phosphor could find applications in medical and lamp industry.
Macromolecular Symposia, 2019
The polycrystalline powder sample of Bi 3+-activated strontium yttrium borate phosphor Sr 3 Y 1−x... more The polycrystalline powder sample of Bi 3+-activated strontium yttrium borate phosphor Sr 3 Y 1−x (BO 3) 3 : x Bi 3+ (x = 3, 4, 5 mole%) is prepared by solution combustion technique. Formation of phosphor in the desired crystalline phase is confirmed by powder X-ray diffraction characterization and FTIR, SEM images of the synthesized phosphor show the irregular grains with average particle size 2.5 µm. Luminescence properties of the synthesized phosphor are investigated at room temperature. The excitation spectrum consists of a single broad absorption band from 200 to 370 nm with the prominent excitation peak at 336 nm [ 1 S 0 to 3 P 1 of Bi 3+ ions] and weak excitation peak at 254 nm [ 1 S 0 to 1 P 1 of Bi 3+ ions]. Strongest emission peak of 492 nm wavelength that is of blue light is observed at 336 nm UV light excitation. Sr 3 Y 1−x (BO 3) 3 : x Bi 3+ phosphor emits blue light. As Bi 3+ is sensitive to the surrounding crystal field environment it shows weak excitation peak at 254 nm, which gives emission at 413 nm. Hence, Sr 3 Y 1−x (BO 3) 3 : x Bi 3+ is new UV excited blue emitting phosphor useful for UV/blue chip WLEDs.
ABSTRACT In the present work we report the preparation and photoluminescence characteristics of D... more ABSTRACT In the present work we report the preparation and photoluminescence characteristics of Dy3+ doped borate phosphor K2Al2B2O7:Dy3+. The fine polycrystalline powder samples of K2Al2B2O7:Dy3+ has been prepared by a novel combustion technique. This method is based on the exothermic redox reaction involves, metal nitrates and organic fuel (urea). The formation of samples was confirmed by powder XRD technique. The photoluminescence properties of borate phosphors have been investigated on fluorescence spectrometer (F-7000). The PL excitation spectra of K2Al2B2O7:Dy3+ consists of several bands peaking at 241 nm, 297 nm, 324 nm, 350 nm, 364 nm and 387 nm. Since the prominent excitation peaks are above 360nm, the phosphor may useful for solid state lighting application. The emission spectrum monitored at 351 nm excitation consists of blue emission band peaking at 481 nm and yellow emission band peaking at 574nm.
Journal of Luminescence, 2013
A combustion synthesis method has been developed for synthesis of Eu 2+ doped CaAlSiN3 phosphor a... more A combustion synthesis method has been developed for synthesis of Eu 2+ doped CaAlSiN3 phosphor and its photoluminescence properties were investigated. Ca, Al, Si, and Eu2O3 powders were used as the Ca, Al, Si and Eu sources. The addition of NaN3, NH4Cl and Si3N4 powders was found to increase significantly the product yield. These powders were mixed and pressed into a compact, which was then wrapped up with an igniting agent (i.e., Mg+Fe3O4). The compact was ignited by electrical heating under a N2 pressure of ≤1.0 MPa. Effects of these experimental parameters on the product yield were investigated and a reaction mechanism was proposed. The synthesized CaAlSiN3:Eu 2+ phosphor absorbs light in the region of 200-600 nm and shows a broad band emission in the region of 500-800 nm due to the 4f 6 5d 1 → 4f 7 transition of Eu 2+. The sample doped with Eu 2+ at the optimized molar ratio of 0.04 is efficiently excited by the blue light (460 nm) and generates emission peaking at ~650 nm with peak emission intensity ~106% of a commercially available phosphor, YAG:Ce 3+ (P46-Y3).The internal quantum efficiency of the synthesized phosphor was measured to be 71%, compared to 69% of the YAG:Ce 3+ (P46-Y3).
Journal of Alloys and Compounds, 2014
Optically efficient terbium activated alkaline earth metal tungstate nano phosphors (AWO 4 [A = C... more Optically efficient terbium activated alkaline earth metal tungstate nano phosphors (AWO 4 [A = Ca, Sr]) with different doping concentrations have been prepared by mechanochemically assisted solid state metathesis reaction at room temperature for the first time. The prepared phosphors were characterized by the X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscope (SEM), Fourier transform Raman (FT-Raman) spectroscopy, photoluminescence and diffuse reflectance spectroscopy measurements. The XRD and Raman spectra results showed that the prepared powders present a scheelite-type tetragonal structure. FTIR spectra exhibited a high absorption band situated at around 850 cm-1 , which was ascribed to the W-O antisymmetric stretching vibrations into the [WO 4 ] 2tetrahedron groups and the SEM images reveal that the particle sizes were in the range of 20-60 nm. The excitation and the emission spectra were measured to characterize the luminescent properties of the phosphors. The excitation spectrum exhibits a charge transfer broad band along with some sharp peaks from the typical 4f-4f transitions of Tb 3?. Under excitation of UV light, these AWO 4 :xTb 3? (A = Ca, Sr) phosphors showed a strong emission band centered at 545 nm (green) which corresponds to 5 D 4 ? 7 F 5 transition of Tb 3?. Analysis of the emission spectra with different Tb 3? concentrations revealed that the optimum dopant concentration for CaWO 4 :xTb 3? and SrWO 4 :xTb 3? phosphors are about 8 and 6 mol% of Tb 3?. The green emission intensity of the solid state meta-thesis prepared CaWO 4 :0.08Tb 3? and SrWO 4 :0.06Tb 3? phosphors are 1.5 and 1.2 times greater than that of the commercial LaPO 4 :Ce, Tb green phosphor. All properties show that AWO 4 :Tb 3? (A = Ca, Sr) is a very appropriate green-emitting phosphor for fluorescent lamp applications.
Optik, 2015
Abstract This paper reports reduction of Eu 3+ → Eu 2+ in BaAl 2 B 2 O 7 host prepared in an oxi... more Abstract This paper reports reduction of Eu 3+ → Eu 2+ in BaAl 2 B 2 O 7 host prepared in an oxidizing environment by modified solution combustion synthesis technique. The crystal phase and surface morphology of the prepared phosphor have been studied by powder X-ray diffraction (XRD) and FE-SEM images, respectively. Photoluminescence emission spectra of BaAl 2 B 2 O 7 :Eu 2+ exhibits a strong emission band peaking at 375 nm (UV-A region), upon excited by 309 nm near UV light. For lower concentrations of Eu 2+ , the emission intensity of BaAl 2 B 2 O 7 :Eu 2+ was measured. This phosphor could find applications in medical and lamp industry.