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Singh, Vijay,Sivaramaiah, G.,Singh, N.,Rao, J. L.,Dubey, Vikas,Singh, Pramod K. Springer-Verlag 2018 Journal of materials science. Materials in electro Vol.29 No.8
<P>Fe-doped CaAl12O19 was prepared via a simple combustion route. The formation of the as-prepared and post-heated combustion products was confirmed using an XRD analysis. The EPR spectrum of this sample exhibited a number of resonance signals. The paramagnetic centers have been quantified at different g factors in the range of 19.3-1.14. These resonance signals are attributed to pairs of Fe3+ ions. The resonance signal at a g value of similar to 4.2 is attributed to the axial-symmetry tetrahedral site. The resonance signal at a g value of similar to 2.0 is attributed to the presence of Fe3+ ions in an axial-symmetry octahedral site. The EPR parameters of the post-heated CaAl12O19:Fe3+ sample at room temperature and 110 K were calculated and compared.</P>
Singh, Vijay,Pathak, M.S.,Singh, N.,Dubey, Vikas,Singh, Pramod K. Elsevier 2018 Optik Vol.152 No.-
<P><B>Abstract</B></P> <P>LiAl<SUB>5</SUB>O<SUB>8</SUB> doped with varying concentrations of Ce<SUP>3+</SUP> were synthesized by a combustion route. Powder X-ray diffraction and scanning electron microscopy techniques were used to characterize the as-prepared and annealed phosphors. The luminescence intensity decreased after annealing the samples at 800°C for 2h in air. These results indicate the possibility of fabrication of high quality Ce<SUP>3+</SUP> doped LiAl<SUB>5</SUB>O<SUB>8</SUB> phosphor even at furnace temperature 500°C via a simple process.</P>
Singh, Vijay,Singh, N.,Pathak, M.S.,Dubey, Vikas,Singh, Pramod K. Elsevier 2018 Optik Vol.155 No.-
<P><B>Abstract</B></P> <P>ZnAl<SUB>2</SUB>O<SUB>4</SUB> doped with varying concentrations of cerium phosphors were synthesized by combustion synthesis route. Two types of powder samples were examined: as-prepared and annealed at 800°C in air atmosphere. We investigated the structural, morphological and photoluminescence properties of cerium doped ZnAl<SUB>2</SUB>O<SUB>4</SUB> phosphors. Results of scanning electron microscopy, X-ray diffraction, photoluminescence investigations were presented.</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>
UV emission from Gd<sup>3+</sup> ions in LaAl<sub>11</sub>O<sub>18</sub> phosphors
Singh, Vijay,Singh, N.,Pathak, M.S.,Watanabe, S.,Gundu Rao, T.K.,Singh, Pramod K.,Dubey, Vikas Elsevier 2018 Optik Vol.157 No.-
<P><B>Abstract</B></P> <P>Phosphors with the composition La<SUB>1-x</SUB>Gd<SUB>x</SUB>Al<SUB>11</SUB>O<SUB>18</SUB> (x = 0.01–0.10) were synthesized by combustion at a furnace temperature of 500 °C. The formation of the as-prepared combustion products was confirmed by X-ray diffraction analysis. On excitation with 273 nm, an emission band for the Gd<SUP>3+</SUP> ion was observed at 314 nm. This band progressively enhanced with increasing Gd<SUP>3+</SUP> concentration. The phosphor with low concentrations of Gd<SUP>3+</SUP> ions exhibits prominent ESR lines with <I>g</I> <SUB>eff</SUB> ∼ 1.9, 2.0, 4.7, and 5.9. With high dopant concentrations, the spectrum shows features similar to those of a U-spectrum with dominant lines with <I>g</I> <SUB>eff</SUB> ∼ 2.0, 2.9, 4.6, and 6.1. Low field lines arise from distortions in the immediate environment of the Gd<SUP>3+</SUP> ion.</P>
Visible upconversion in Er<sup>3+</sup>/Yb<sup>3+</sup> co-doped LaAlO<sub>3</sub> phosphors
Singh, Vijay,Rai, V.K.,Singh, N.,Pathak, M.S.,Rathaiah, M.,Venkatramu, V.,Patel, Rahul V.,Singh, Pramod K.,Dhoble, S.J. Elsevier 2017 Spectrochimica acta. Part A, Molecular and biomole Vol.171 No.-
<P><B>Abstract</B></P> <P>The Er<SUP>3+</SUP> doped and Er<SUP>3+</SUP>/Yb<SUP>3+</SUP> co-doped LaAlO<SUB>3</SUB> phosphors have been synthesized by the combustion method and characterized their structural, morphological, elemental, vibrational and optical properties. The optical absorption and upconversion properties of the synthesized phosphors have been studied. Upon co-doping Yb<SUP>3+</SUP> ions into Er<SUP>3+</SUP>:LaAlO<SUB>3</SUB>, the blue, green and red upconversion emissions of Er<SUP>3+</SUP> ions have been enhanced about ~20, ~54 and ~22 times, under 978nm laser excitation. The observed upconversion emissions could be due to excited state absorption in Er<SUP>3+</SUP>:LaAlO<SUB>3,</SUB> whereas energy transfer is dominant mechanism in Er<SUP>3+</SUP>/Yb<SUP>3+</SUP>:LaAlO<SUB>3</SUB> phosphors. The tuning in the color emitted from the synthesized phosphors towards the green region has been found due to incorporation of the Yb<SUP>3+</SUP> ions. With increase in the pump power, the color emitted from the co-doped phosphor is not tuned significantly, showing its applicability in making the green display devices.</P> <P><B>Highlights</B></P> <P> <UL> <LI> By facile combustion synthesis, Er<SUP>3+</SUP> and Er<SUP>3+</SUP>/Yb<SUP>3+</SUP> doped LaAlO<SUB>3</SUB> phosphors are obtained. </LI> <LI> Phosphor was characterized using XRD, SEM-EDX, FTIR and Up-conversion spectroscopy. </LI> <LI> Upon excitation at 978nm, intense up-conversion emission is observed. </LI> <LI> Prepared materials could be suitable for up-conversion lasers and green display device. </LI> </UL> </P> <P><B>Graphical Abstract</B></P> <P>[DISPLAY OMISSION]</P>
Singh, Vijay,Singh, N.,Pathak, M.S.,Singh, Pramod K.,Natarajan, V. Elsevier 2018 Optik Vol.171 No.-
<P><B>Abstract</B></P> <P>Tb<SUP>3+</SUP>-doped Ca<SUB>2</SUB>La<SUB>8</SUB>(SiO<SUB>4</SUB>)<SUB>6</SUB>O<SUB>2</SUB> phosphors with different Tb<SUP>3+</SUP> content powders were successfully synthesized using the sol-gel process for this paper. A series of green-emitting Tb<SUP>3+</SUP>-doped Ca<SUB>2</SUB>La<SUB>8</SUB>(SiO<SUB>4</SUB>)<SUB>6</SUB>O<SUB>2</SUB> phosphors was well characterized using the XRD and PL techniques. The emission measurements upon a UV-light excitation of 232 nm showed the Tb<SUP>3+</SUP>-emission characteristics. The emission and excitation spectra were recorded as the Tb<SUP>3+</SUP> concentration was varied. It became evident that the addition of the Tb<SUP>3+</SUP> increased the PL intensity, and the reasons for this behavior are discussed.</P>
Singh, Vijay,Singh, N.,Dubey, Vikas,Singh, Pramod K.,Shinde, K.N.,Ravi Kanth Kumar, V.V. Elsevier 2018 OPTIK -STUTTGART- Vol.158 No.-
<P><B>Abstract</B></P> <P>Ce<SUP>3+</SUP>-doped CaAl<SUB>12</SUB>O<SUB>19</SUB> phosphors with different Ce<SUP>3+</SUP> contents, as well as those with Mg<SUP>2+</SUP> codoped powders, were successfully synthesized using a rapid combustion method (<5 min) for this paper. The powders were well characterized by the X-ray diffraction (XRD) and photoluminescence (PL) techniques. The emission measurements upon a UV-light excitation (262 nm) showed the emission characteristics of the Ce<SUP>3+</SUP> ion that are due to the 5d–4 f transitions. The emission and excitation spectra were recorded as the Ce<SUP>3+</SUP> concentration was kept constant and the Mg<SUP>2+</SUP> concentration was varied. It became evident that the addition of the Mg<SUP>2+</SUP> along with the Ce<SUP>3+</SUP> resulted in increases of the PL intensity, and the reasons for this behavior are discussed.</P>