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Luminescence and defect centres in MgSrAl<sub>10</sub>O<sub>17</sub>:Sm<sup>3+</sup> phosphor
Singh, Vijay,Watanabe, S.,Gundu Rao, T.K.,Chubaci, J.F.D,Kwak, Ho-Young Elsevier 2010 Journal of non-crystalline solids Vol.356 No.23
<P><B>Abstract</B></P><P>An efficient reddish orange emission MgSrAl<SUB>10</SUB>O<SUB>17</SUB>:Sm<SUP>3+</SUP> phosphor was prepared by the combustion method. The phosphor has been characterized by X-ray diffraction, scanning electron microscopy, thermogravimetric analysis measurements. Photoluminescence spectrum revealed that samarium ions are present in trivalent oxidation states. The phosphor exhibits two thermally stimulated luminescence (TSL) peaks at 210°C and 450°C. Electron spin resonance studies were carried out to identify the defect centres responsible for the TSL process in MgSrAl<SUB>10</SUB>O<SUB>17</SUB>:Sm<SUP>3+</SUP> phosphor. Three defect centres have been identified in irradiated phosphor and these centres are tentatively assigned to an O<SUP>−</SUP> ion and F<SUP>+</SUP> centres. O<SUP>−</SUP> ion (hole centre) correlates with the 210°C TSL peak while one of the F<SUP>+</SUP> centres (electron centre) appears to relate to the 450°C TSL peak.</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>
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>
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>
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,Sivaramaiah, G.,Rao, J.L.,Kim, S.H. Elsevier 2015 Journal of luminescence Vol.157 No.-
<P><B>Abstract</B></P> <P>The UV-emitting Y<SUB>4</SUB>Zr<SUB>3</SUB>O<SUB>12</SUB>:Gd phosphor has been prepared via a solution combustion method. This phosphor sample has been characterized by X-ray diffraction, scanning electron microscopy, diffuse reflectance, photoluminescence and electron spin resonance (EPR) spectroscopic techniques. Phase analysis indicates that the obtained product has a rhombohedral structure. Platelet like structures are obtained with non-uniform distribution. The emission spectrum, upon 274nm excitation exhibits a well-defined sharp and intense peak centered at 313nm emitting UV light. The EPR spectrum exhibits several resonance signals with the effective <I>g</I> values at <I>g</I> ≈5.58, 4.33, 3.51, 2.73 and 1.98. From EPR and optical studies, it is observed that gadolinium ions are present in trivalent state in the Y<SUB>4</SUB>Zr<SUB>3</SUB>O<SUB>12</SUB> matrix.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The rhombohedral phase of Y<SUB>4</SUB>Zr<SUB>3</SUB>O<SUB>12</SUB> could be obtained via the facile combustion method. </LI> <LI> The narrow-band ultraviolet B emission due to Gd<SUP>3+</SUP> ions were observed. </LI> <LI> EPR studies have confirmed the presence of Gd<SUP>3+</SUP> ions in the sample. </LI> </UL> </P>