Abstract A series of Er 3+ doped CaB 2 O 4 phosphors were synthesized by conventional solid state... more Abstract A series of Er 3+ doped CaB 2 O 4 phosphors were synthesized by conventional solid state reaction method. XRD and FTIR spectra confirmed the crystal phase formation of CaB 2 O 4 :Er 3+ , Li + phosphor. Structural and morphological studies were carried out using transmission electron microscopy and scanning electron microscopy. UV–vis-NIR optical absorption spectrum of CaB 2 O 4 :Er 3+ , Li + phosphor was analyzed on the basis of Judd-Ofelt theory. Spontaneous emission transition probabilities and branching ratios were evaluated using Judd-Ofelt intensity parameters. Excitation spectra reveal strong transitions from the ground state 4 I 15/2 of Er 3+ ions. Dependence of Er 3+ doping concentration on the luminescence properties of the phosphor was systematically investigated under the excitation wavelengths 407 and 980 nm. Emission spectra consist of characteristic emission peaks of Er 3+ at 550 nm ( 4 S 3/2 → 4 I 15/2 ), 663 nm ( 4 F 9/2 → 4 I 15/2 ) and 770 nm ( 4 I 9/2 → 4 I 15/2 ) in visible and 1531 nm ( 4 I 13/2 → 4 I 15/2 ) in NIR regions. Dependence of Er 3+ ion concentration on emission intensity suggests concentration quenching in the prepared phosphor sample and also suggests the possible interaction type dipole–dipole among rare earth ions. From the luminescence decay analysis excited state life time of rare earth ion is found to be 6.92 μs. The calculated CIE color coordinates lies in the greenish yellow region. Since the prepared phosphor gives emission in green-red and NIR regions they might have potential application in LEDs and lasers.
Abstract A series of Eu3+ doped Ba2Sb2O7 phosphors were prepared by the solid-state reaction meth... more Abstract A series of Eu3+ doped Ba2Sb2O7 phosphors were prepared by the solid-state reaction method. XRD analysis confirmed its orthorhombic structure with the space group Imma. The photoluminescence spectra implies that the phosphors exhibit characteristic emission peaks corresponding to 5D0→7FJ transitions of Eu3+ ions under NUV excitation. The CIE chromaticity coordinates reveal reddish-orange emission in the warm CCT region with high color purity. The mechanism for concentration quenching was found to be quadrupole-quadrupole interaction and the decay lifetime of the phosphors is in the millisecond range. The results suggest that the prepared phosphors are a potential candidate for phosphor-converted white light-emitting diodes and optoelectronic devices
Abstract Tunable white light-emitting Ca(2-x)Sb2O7:xDy3+ phosphors were synthesized via high temp... more Abstract Tunable white light-emitting Ca(2-x)Sb2O7:xDy3+ phosphors were synthesized via high temperature solid-state reaction method. The crystal structure, morphology, luminescence characteristics, and energy transfer mechanism of the phosphors were investigated using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), high resolution transmission electron microscopy (HR-TEM), UV–Visible spectroscopy, photoluminescence (PL) spectroscopy, and Fluorescence lifetime analysis. The XRD, EDS, and TEM analysis confirmed the phase purity and orthorhombic weberite structure of the samples with an average particle size in the range of 0.2 to 0.3 μm. Under ultraviolet (UV) excitation of 330/351 nm, the prepared phosphors exhibit characteristic emission bands of Dy3+ ions along with the blue emission band of the host. The broad band peaking at 440 nm corresponds to Sb5+ to O2− transition of host and the peaks at 477, 575, and 670 nm originates from 4F9/2 → 6H15/2, 4F9/2 → 6H13/2 and 4F9/2 → 6H11/2 transitions of Dy3+ ions respectively. There exists efficient energy transfer from Ca2Sb2O7 host to Dy3+ ions and the energy transfer efficiency increases with an increase in Dy3+ ion concentration. Using Dexter’s theory, the mechanism of energy transfer was found to be dipole-quadrupole interaction and the energy transfer process is explained in detail. The decay lifetime of Dy3+ ions was estimated to be in the microsecond range. The critical distance for concentration quenching is determined to be 13.807 A and the dominant mechanism is dipole-dipole interaction. The calculated Commission International de L’Eclairng (CIE) coordinates and correlated color temperature (CCT) values imply that the emission color can be tuned from blue (0.144, 0.097) to near-white (0.296, 0.292) in the cool CCT region. The results suggest that Dy3+ doped Ca2Sb2O7 phosphor is a potential candidate for solid-state lighting and display fields.
Abstract A series of Dy3+ doped CaB2O4 phosphors were synthesized by conventional solid state rea... more Abstract A series of Dy3+ doped CaB2O4 phosphors were synthesized by conventional solid state reaction method. XRD analysis reveals that the crystal structure of the sample was well matched with the orthorhombic CaB2O4. FTIR spectra characterize various vibrational bonds present in the samples. SEM images indicate that the prepared phosphor have microstructure nature with irregular morphology. UV-Vis-NIR optical absorption spectrum of CaB2O4:Dy3+, Li+ phosphor was analyzed on the basis of Judd-Ofelt theory and the J-O intensity parameters (Ωλ) were evaluated. The radiative properties such as transition probability (AR), stimulated emission cross-section (σe) etc. were calculated. Excitation spectra reveal strong transitions from the ground state 6H15/2 of Dy3+ ions. The prepared phosphor samples provide emission in blue (4F9/2 → 6H15/2), yellow (4F9/2 → 6H13/2) and red (4F9/2 → 6H11/2) regions under an excitation wavelength of 350 nm. The alkali metal Li+ was added to maintain the charge neutrality of the phosphor system which also enhances the luminescence intensity of Dy3+ ions. CIE chromaticity studies show that the prepared phosphor samples are exhibiting near white light emission and corresponding correlated color temperature (CCT) were appearance in cool region. The results suggest that as-synthesized phosphors have potential application in the field of NUV white light emitting diodes (W-LEDs).
Abstract This paper reports the synthesis of Dy3+/Er3+/Sm3+ ions singly and triply doped with mul... more Abstract This paper reports the synthesis of Dy3+/Er3+/Sm3+ ions singly and triply doped with multicomponent borosilicate glasses by conventional melt quench technique. Presence of an additional excitation band at 374 nm in the excitation spectrum corresponding to Dy3+ (λemi = 574 nm) reveals the possibility of obtaining the fluorescence spectra of Dy3+, Er3+, and Sm3+ together and predicts the presence of energy transfer in the prepared triply doped glassy system. Surprisingly, the luminescent bands owing to Dy3+, Er3+, and Sm3+ ions were observed in every luminescence spectra recorded with 374, 379, and 400 nm excitation wavelengths. The intensity of Dy3+ and Er3+ emission peaks showed a remarkable decrement with an increase in Sm3+ concentration, while Sm3+ bands seemed to be enhanced monotonously. The recorded emission intensities were further characterized by using CIE diagram and obtained CIE coordinates and CCT values recommend the glasses for cool or warm near white light emitting applications.
Abstract A series of Er 3+ doped CaB 2 O 4 phosphors were synthesized by conventional solid state... more Abstract A series of Er 3+ doped CaB 2 O 4 phosphors were synthesized by conventional solid state reaction method. XRD and FTIR spectra confirmed the crystal phase formation of CaB 2 O 4 :Er 3+ , Li + phosphor. Structural and morphological studies were carried out using transmission electron microscopy and scanning electron microscopy. UV–vis-NIR optical absorption spectrum of CaB 2 O 4 :Er 3+ , Li + phosphor was analyzed on the basis of Judd-Ofelt theory. Spontaneous emission transition probabilities and branching ratios were evaluated using Judd-Ofelt intensity parameters. Excitation spectra reveal strong transitions from the ground state 4 I 15/2 of Er 3+ ions. Dependence of Er 3+ doping concentration on the luminescence properties of the phosphor was systematically investigated under the excitation wavelengths 407 and 980 nm. Emission spectra consist of characteristic emission peaks of Er 3+ at 550 nm ( 4 S 3/2 → 4 I 15/2 ), 663 nm ( 4 F 9/2 → 4 I 15/2 ) and 770 nm ( 4 I 9/2 → 4 I 15/2 ) in visible and 1531 nm ( 4 I 13/2 → 4 I 15/2 ) in NIR regions. Dependence of Er 3+ ion concentration on emission intensity suggests concentration quenching in the prepared phosphor sample and also suggests the possible interaction type dipole–dipole among rare earth ions. From the luminescence decay analysis excited state life time of rare earth ion is found to be 6.92 μs. The calculated CIE color coordinates lies in the greenish yellow region. Since the prepared phosphor gives emission in green-red and NIR regions they might have potential application in LEDs and lasers.
Abstract A series of Eu3+ doped Ba2Sb2O7 phosphors were prepared by the solid-state reaction meth... more Abstract A series of Eu3+ doped Ba2Sb2O7 phosphors were prepared by the solid-state reaction method. XRD analysis confirmed its orthorhombic structure with the space group Imma. The photoluminescence spectra implies that the phosphors exhibit characteristic emission peaks corresponding to 5D0→7FJ transitions of Eu3+ ions under NUV excitation. The CIE chromaticity coordinates reveal reddish-orange emission in the warm CCT region with high color purity. The mechanism for concentration quenching was found to be quadrupole-quadrupole interaction and the decay lifetime of the phosphors is in the millisecond range. The results suggest that the prepared phosphors are a potential candidate for phosphor-converted white light-emitting diodes and optoelectronic devices
Abstract Tunable white light-emitting Ca(2-x)Sb2O7:xDy3+ phosphors were synthesized via high temp... more Abstract Tunable white light-emitting Ca(2-x)Sb2O7:xDy3+ phosphors were synthesized via high temperature solid-state reaction method. The crystal structure, morphology, luminescence characteristics, and energy transfer mechanism of the phosphors were investigated using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), high resolution transmission electron microscopy (HR-TEM), UV–Visible spectroscopy, photoluminescence (PL) spectroscopy, and Fluorescence lifetime analysis. The XRD, EDS, and TEM analysis confirmed the phase purity and orthorhombic weberite structure of the samples with an average particle size in the range of 0.2 to 0.3 μm. Under ultraviolet (UV) excitation of 330/351 nm, the prepared phosphors exhibit characteristic emission bands of Dy3+ ions along with the blue emission band of the host. The broad band peaking at 440 nm corresponds to Sb5+ to O2− transition of host and the peaks at 477, 575, and 670 nm originates from 4F9/2 → 6H15/2, 4F9/2 → 6H13/2 and 4F9/2 → 6H11/2 transitions of Dy3+ ions respectively. There exists efficient energy transfer from Ca2Sb2O7 host to Dy3+ ions and the energy transfer efficiency increases with an increase in Dy3+ ion concentration. Using Dexter’s theory, the mechanism of energy transfer was found to be dipole-quadrupole interaction and the energy transfer process is explained in detail. The decay lifetime of Dy3+ ions was estimated to be in the microsecond range. The critical distance for concentration quenching is determined to be 13.807 A and the dominant mechanism is dipole-dipole interaction. The calculated Commission International de L’Eclairng (CIE) coordinates and correlated color temperature (CCT) values imply that the emission color can be tuned from blue (0.144, 0.097) to near-white (0.296, 0.292) in the cool CCT region. The results suggest that Dy3+ doped Ca2Sb2O7 phosphor is a potential candidate for solid-state lighting and display fields.
Abstract A series of Dy3+ doped CaB2O4 phosphors were synthesized by conventional solid state rea... more Abstract A series of Dy3+ doped CaB2O4 phosphors were synthesized by conventional solid state reaction method. XRD analysis reveals that the crystal structure of the sample was well matched with the orthorhombic CaB2O4. FTIR spectra characterize various vibrational bonds present in the samples. SEM images indicate that the prepared phosphor have microstructure nature with irregular morphology. UV-Vis-NIR optical absorption spectrum of CaB2O4:Dy3+, Li+ phosphor was analyzed on the basis of Judd-Ofelt theory and the J-O intensity parameters (Ωλ) were evaluated. The radiative properties such as transition probability (AR), stimulated emission cross-section (σe) etc. were calculated. Excitation spectra reveal strong transitions from the ground state 6H15/2 of Dy3+ ions. The prepared phosphor samples provide emission in blue (4F9/2 → 6H15/2), yellow (4F9/2 → 6H13/2) and red (4F9/2 → 6H11/2) regions under an excitation wavelength of 350 nm. The alkali metal Li+ was added to maintain the charge neutrality of the phosphor system which also enhances the luminescence intensity of Dy3+ ions. CIE chromaticity studies show that the prepared phosphor samples are exhibiting near white light emission and corresponding correlated color temperature (CCT) were appearance in cool region. The results suggest that as-synthesized phosphors have potential application in the field of NUV white light emitting diodes (W-LEDs).
Abstract This paper reports the synthesis of Dy3+/Er3+/Sm3+ ions singly and triply doped with mul... more Abstract This paper reports the synthesis of Dy3+/Er3+/Sm3+ ions singly and triply doped with multicomponent borosilicate glasses by conventional melt quench technique. Presence of an additional excitation band at 374 nm in the excitation spectrum corresponding to Dy3+ (λemi = 574 nm) reveals the possibility of obtaining the fluorescence spectra of Dy3+, Er3+, and Sm3+ together and predicts the presence of energy transfer in the prepared triply doped glassy system. Surprisingly, the luminescent bands owing to Dy3+, Er3+, and Sm3+ ions were observed in every luminescence spectra recorded with 374, 379, and 400 nm excitation wavelengths. The intensity of Dy3+ and Er3+ emission peaks showed a remarkable decrement with an increase in Sm3+ concentration, while Sm3+ bands seemed to be enhanced monotonously. The recorded emission intensities were further characterized by using CIE diagram and obtained CIE coordinates and CCT values recommend the glasses for cool or warm near white light emitting applications.
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