http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
EPR and optical investigations of LaMgAl<sub>11</sub>O<sub>19</sub>:Cr<sup>3+</sup> phosphor
Singh, V.,Sivaramaiah, G.,Rao, J.L.,Kim, S.H. Pergamon Press 2014 Materials research bulletin Vol.60 No.-
The LaMgAl<SUB>11</SUB>O<SUB>19</SUB>:Cr<SUP>3+</SUP> phosphor has been prepared by a low-temperature combustion synthesis method. As-prepared combustion synthesized powder was characterized using powder X-ray diffraction (XRD), diffuse reflectance (DRS), electron paramagnetic resonance (EPR) and photoluminescence (PL) studies. The X-ray diffraction pattern reveals crystalline hexagonal phases. The UV-vis diffuse reflectance spectrum exhibits three broad bands characteristic of Cr<SUP>3+</SUP> ions in octahedral symmetry. The EPR spectrum exhibits several resonance signals. The signals with the effective g values at g=4.84, 3.64 and 2.26 have been attributed to the isolated Cr<SUP>3+</SUP> ions. The signal with the effective g value at g=1.94 has been attributed to exchange coupled Cr<SUP>3+</SUP>-Cr<SUP>3+</SUP> ion pairs. The PL studies exhibit several bands characteristic of Cr<SUP>3+</SUP> ions in octahedral symmetry.
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>
EPR and PL studies on UVB-emitting gadolinium-doped SrAl<sub>12</sub>O<sub>19</sub> phosphors
Singh, Vijay,Sivaramaiah, G.,Singh, N.,Rao, J.L.,Singh, Pramod K.,Pathak, M.S.,Hakeem, D.A. Elsevier 2018 Optik Vol.158 No.-
<P><B>Abstract</B></P> <P>A series of UV-emitting Gd-doped SrAl<SUB>12</SUB>O<SUB>19</SUB> phosphors were prepared using a low-temperature solution-combustion method for which urea served as the fuel. These phosphors were characterized using X-ray diffraction (XRD), electron paramagnetic resonance (EPR), and photoluminescence (PL) studies. In phosphors with low dopant concentrations, the EPR spectrum exhibited resonance signals at the effective g factors of 2.41, 2.17, 1.99, 1.88, and 1.66. With the increasing of the concentrations, the resonance signals are evident at the effective g factors of 2.39, 2.18, 1.95, and 1.65. The PL studies of the samples showed a dominant emission peak at 312 nm that corresponds to the <SUP>6</SUP>P<SUB>7/2</SUB> → <SUP>8</SUP>S<SUB>7/2</SUB> transitions of the Gd<SUP>3+</SUP> ions.</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>
Singh, V.,Sivaramaiah, G.,Rao, J. L.,Singh, N.,Mohapatra, M.,Singh, P. K.,Pathak, M. S.,Dhoble, S. J. Minerals, Metals & Materials Society and the Insti 2017 Journal of Electronic Materials Vol. No.
<P>LiAl5O8 doped with Fe was synthesized by a propellant combustion route at furnace temperature of 773 K. The phosphor was characterized using powder x-ray diffraction, optical absorption, electron paramagnetic resonance (EPR) and photoluminescence spectroscopic techniques. The optical absorption spectrum exhibits a broad band at 242 nm characteristic of charge transfer between Fe3+-O2-. On excitation with 293 nm, emission band for the Fe3+ ion was observed at 687 nm. The CIE (International Commission on Illumination or Commission Internationale de l'Elcairage) coordinates for the system were evaluated adopting standard procedure which suggested that the system can be effective as a deep red emitting phosphor. The EPR spectrum of this phosphor exhibits a number of resonance signals characteristic of Fe3+ ions. The resonance signals at g = 3.16, 2.27 are attributed to Fe3+ present at tetrahedral site with an axial symmetry. The resonance signals at g = 1.98 and 1.43 are attributed to Fe3+ ions in octahedral site with an axial symmetry. Various EPR parameters such as the number of spins, Gibbs free energy, magnetic susceptibility, Curie constant and effective magnetic moment values are calculated and compared at room temperature and 110 K.</P>
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>
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>
Singh, N.,Sivaramaiah, G.,Rao, J.L.,Watanabe, S.,Rao, T.K. Gundu,Patel, R.V.,Singh, Vijay Elsevier 2017 Journal of luminescence Vol.188 No.-
<P><B>Abstract</B></P> <P>Gadolinium activated UV-emitting ZrO<SUB>2</SUB> phosphor has been prepared by combustion synthesis. The prepared phosphor was characterized using X-ray diffraction, scanning electron microscopy and energy dispersive X-ray techniques. The optical absorption spectrum in the 200−500nm region and excitation spectrum corresponding to the emission at 314nm for ZrO<SUB>2</SUB>:Gd<SUP>3+</SUP> phosphor has been recorded. Gd<SUP>3+</SUP> doped ZrO<SUB>2</SUB> displays electron spin resonance signals with effective g values at <I>g</I>≈1.9, 2.4 and 4.1. Low field signals are attributed to Gd<SUP>3+</SUP> ion located in distorted surroundings experiencing a relatively strong crystal field due to the proximity of charge compensator oxygen vacancies.</P>
Singh, V.,Sivaramaiah, G.,Rao, J. L.,Singh, N.,Srivastava, A. K.,Singh, P. K.,Pawar, S. U.,Gao, H.,Mardina, P. Springer Science + Business Media 2016 Journal of materials science Materials in electron Vol.27 No.5
<P>Fe doped CeO2 powder was prepared using solution combustion method. Powder X-ray diffraction and scanning electron microscopy methods are used to characterize the combustion derived powder. The optical absorption spectrum exhibits three bands due to Fe3+ and Fe2+ ions. Electron paramagnetic resonance (EPR) spectrum of this sample exhibits number of resonance signals due to Fe3+ ions. The number of spins (N) participating in resonance and its paramagnetic susceptibility (chi) has been evaluated. From EPR and optical studies it is observed that iron ions are present in trivalent state.</P>