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Cr3+-Doped Yb3Ga5O12 Nanophosphor: Synthesis, Optical, EPR, Studies
Singh, V.,Sivaramaiah, G.,Rao, J. L.,Singh, N.,Pathak, M. S.,Jirimali, H. D.,Singh, P. K.,Srivastava, A. K.,Dhoble, S. J.,Mohapatra, M. Springer Science + Business Media 2016 Journal of electronic materials Vol.45 No.8
<P>Gallium garnets of lanthanides are multifunctional materials especially known for their complicated structure and magnetic properties. In addition, with a suitable transition metal dopant ion, these matrices have been proved to be excellent materials for lasers. In particular, gallium garnet of ytterbium (Yb3Ga5O12) is known to possess excellent properties with regards to these applications. In this connection, Yb3Ga5O12 doped with Cr3+ nanophosphors were synthesized by a solution combustion route. The synthesized material was characterized by powder x-ray diffraction and scanning electron microscopy for phase purity and homogenous morphology. In order to ascertain the oxidation state of the doped ion, diffuse reflectance (DRF), photoluminescence (PL) and electron paramagnetic resonance (EPR) experiments were performed on the sample. The DRF and PL data suggested the stabilisation of the trivalent Cr ion in the matrix. The EPR spectra exhibited two resonance signals with effective g values at g approximate to 7.6 and 4. The EPR data corroborated the DRF and PL results, suggesting the stabilisation of Cr3+ in the matrix at octahedral-type geometries.</P>
Eu2+ and Mn2+ Co-doped BaMgAl10O17 Blue- and Green-Emitting Phosphor: A Luminescence and EPR Study
Singh, V.,Sivaramaiah, G.,Rao, J. L.,Singh, N.,Srivastava, A. K.,Jirimali, H. D.,Li, J.,Gao, H.,Kumaran, R. S.,Singh, P. K. Springer Science + Business Media 2016 Journal of electronic materials Vol.45 No.6
<P>Eu2+ and Mn2+ co-doped BaMgAl10O17 phosphor has been prepared by a solution combustion method. The structural, morphological and compositional analysis of the BaMgAl10O17:Eu2+ and Mn2+ powders have been studied by x-ray diffraction, scanning electron microscopy and energy dispersive x-ray spectroscopy. The electron paramagnetic resonance (EPR) spectrum exhibited resonance signals with the effective g values of g a parts per thousand 4.88 and g a parts per thousand 1.98. The resonance signal with the effective g value of g a parts per thousand 4.88 is characteristic of Eu2+ ions whereas g a parts per thousand 1.98 is due to Mn2+ ions. The number of spins participating in resonance, Gibbs free energy, magnetic susceptibility, Curie constant, effective magnetic moment, zero-field splitting parameter and hyperfine splitting constant have been evaluated. From optical and EPR correlation, it is inferred that Eu2+ and Mn2+ are present in the BaMgAl10O17 matrix.</P>
Investigation of ultraviolet emitting Gd doped Sr<sub>2</sub>MgSi<sub>2</sub>O<sub>7</sub> phosphors
Singh, Vijay,Sivaramaiah, G.,Singh, N.,Pathak, M.S.,Rao, J.L.,Jirimali, H.D.,Natarajan, V. Elsevier 2018 Optik Vol.169 No.-
<P><B>Abstract</B></P> <P>This article deals with the ultraviolet (UV)-emitting gadolinium (Gd)-doped strontium magnesium disilicate (Sr<SUB>2</SUB>MgSi<SUB>2</SUB>O<SUB>7</SUB>) phosphors. A series of the Gd-doped Sr<SUB>2</SUB>MgSi<SUB>2</SUB>O<SUB>7</SUB> phosphors were prepared using a sol-gel method. The powders were well characterized using the X-ray powder diffraction (XRPD) and scanning electron microscope (SEM) techniques. The emission measurements upon a specific UV-light excitation (273 nm) showed the emission characteristics of the Gd<SUP>3+</SUP> that are due to the <SUP>6</SUP>P<SUB>J/2</SUB> → <SUP>8</SUP>S<SUB>7/2</SUB> transition. EPR spectra of the prepared samples indicated the presence of Gd<SUP>3+</SUP> ions in low symmetry sites in this sample.</P>
Singh, Vijay,Pathak, M.S.,Singh, N.,Singh, Pramod K.,Jirimali, H.D. Elsevier 2018 OPTIK -STUTTGART- Vol.168 No.-
<P><B>Abstract</B></P> <P>A series of Tb<SUP>3+</SUP> doped Sr<SUB>2</SUB>La<SUB>8</SUB>(SiO<SUB>4</SUB>)<SUB>6</SUB>O<SUB>2</SUB> phosphors were successfully synthesized via sol-gel method. The formations of sol-gel phosphors were confirmed using powder X-ray diffraction studies. The emission intensity shows the 544 nm (<SUP>5</SUP>D<SUB>4</SUB> → <SUP>7</SUP>F<SUB>5</SUB>) maximum that was obtained for the prepared samples using the 233 nm excitation. Luminescence quenching was not observed for the prepared series of the Tb<SUP>3+</SUP> doped Sr<SUB>2</SUB>La<SUB>8</SUB>(SiO<SUB>4</SUB>)<SUB>6</SUB>O<SUB>2</SUB> phosphors. The addition of the Tb<SUP>3+</SUP> concentration greatly improved the photoluminescent properties of the present phosphors.</P>
Singh, V.,Mohapatra, M.,Sivaramaiah, G.,Rao, J. L.,Singh, N.,Gao, H.,Li, J.,Srivastava, A. K.,Jirimali, H. D.,Dhoble, S. J. Springer Science + Business Media 2016 Journal of materials science Materials in electron Vol.27 No.4
<P>Manganese doped BaMgAl10O17 nano-phosphors were synthesized by a low-temperature initiated, gas producing solution combustion process. Phase purity of the prepared phosphors was determined using X-ray diffraction technique. Dynamic light scattering technique was used to estimate the average particle size of the synthesized products. Scanning electron microscopy technique was used to study the morphology of the prepared samples. Fourier transform infrared spectroscopy was used to ascertain the formation of the aluminate host. UV-visible absorption spectroscopy showed band maxima at around 260 nm and intense band maxima at around 216 nm. Electron paramagnetic resonance experiments for the system were carried out to understand the site occupancy of the Mn ions. The photoluminescence excitation and emission spectra suggested the stabilisation of Mn ions in Td geometry. From the colour characterisation of the system it was found out that the system can be effective as a green phosphor material with wide range of applications.</P>
Singh, Vijay,Shinde, K.N.,Pathak, M.S.,Singh, N.,Dubey, Vikas,Singh, Pramod K.,Jirimali, H.D. Elsevier 2018 OPTIK -STUTTGART- Vol.164 No.-
<P><B>Abstract</B></P> <P>A series of Tb<SUP>3+</SUP>-doped CaLaAl<SUB>3</SUB>O<SUB>7</SUB> phosphors were successfully synthesized via a sol-gel method. The formation of the synthesized phosphors was confirmed using X-ray powder diffraction (XRPD) studies. A scanning electron microscope (SEM) was used to characterize the surface morphology and to investigate the photoluminescence behaviors in detail. Under the excitation of 235 nm, the emission spectrum consists of the characteristic Tb<SUP>3+</SUP> transitions that mainly peak at 543 nm and correspond to the <SUP>5</SUP>D<SUB>4</SUB> → <SUP>7</SUP>F<SUB>5</SUB> transition. The intensity was greatly improved due to the Tb<SUP>3+</SUP> concentration in the present phosphors. The optimum Tb<SUP>3+</SUP>-doping concentration was determined to be 0.05 mol. The chromaticity coordinates of the CaLaAl<SUB>3</SUB>O<SUB>7</SUB>:Tb<SUP>3+</SUP> were fixed to make it tunable for the blue-to-green region. The typical photographs of the CaLaAl<SUB>3</SUB>O<SUB>7</SUB>:Tb<SUP>3+</SUP> under a 254-nm UV light revealed an intense-green powder. The results showed that this kind of phosphor is potentially applicable in terms of UV-excited white LEDs.</P>