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Synthesis, magnetic and Mossbauer spectroscopic studies of Cr doped lithium ferrite nanoparticles
Srivastava, M.,Layek, S.,Singh, J.,Das, A.K.,Verma, H.C.,Ojha, A.K.,Kim, N.H.,Lee, J.H. Elsevier Sequoia 2014 JOURNAL OF ALLOYS AND COMPOUNDS Vol.591 No.-
Lithium-based ferrites are promising and potential magnetic materials for microwave applications. They possess a spinel (AB<SUB>2</SUB>O<SUB>4</SUB>) type crystal structure, where the distributions of metal cations over the tetrahedral (A) and octahedral (B) voids play a crucial role for exhibiting different physical properties. Among various parameter of synthesis, pH is an important factor that influences the cation distribution over A and B voids, overall growth of the nanoparticles and different physical properties. In the present work single phase Cr substituted lithium ferrite nanoparticles have been synthesized by the sol-gel method at different pH. The phase identification and crystallite size have been probed by X-ray diffraction studies. The crystallite size changes by 44.2-48.8nm upon varying the pH from 3.5 to 11.5. In order to investigate the cations distribution at A/B sites, Mossbauer spectroscopic measurements were done. The values of magnetic hyperfine field obtained from the Mossbauer data for the A and B sites are ~49.5T and 51T, respectively. Moreover, it is observed that the area ratio of B site to A site increases with increasing the pH. This observation further suggests that the B site is more preferable for Fe<SUP>3+</SUP> cations at higher pH than the A site. The magnetic parameter such as saturation magnetization (M<SUB>s</SUB>), remanent magnetization (M<SUB>r</SUB>), coercive field (H<SUB>C</SUB>) and squareness (S) are determined by vibrating sample magnetometer (VSM) measurements, which show a consistent increase with increasing pH. The reason for the variation in magnetic properties has been explained on the basis of increased Fe<SUP>3+</SUP> cation occupancies at the B site and size effect, which is well supported by Mossbauer spectroscopic and XRD studies.
Singh, Deepu,Sinha, B.,Rai, V.P.,Singh, M.N.,Singh, D.K.,Kumar, R.,Singh, A.K. The Korean Society of Plant Pathology 2016 Plant Pathology Journal Vol.32 No.2
Inheritance of resistance to Fusarium wilt (FW) disease caused by Fusarium udum was investigated in pigeonpea using four different long duration FW resistant genotypes viz., BDN-2004-1, BDN-2001-9, BWR-133 and IPA-234. Based on the $F_2$ segregation pattern, FW resistance has been reported to be governed by one dominant gene in BDN-2004-1 and BDN-2001-9, two duplicate dominant genes in BWR-133 and two dominant complimentary genes in resistance source IPA-234. Further, the efficacy of six simple sequence repeat (SSR) markers namely, ASSR-1, ASSR-23, ASSR-148, ASSR-229, ASSR-363 and ASSR-366 reported to be associated with FW resistance were also tested and concluded that markers ASSR-1, ASSR-23, ASSR-148 will be used for screening of parental genotypes in pigeonpea FW resistance breeding programs. The information on genetics of FW resistance generated from this study would be used, to introgress FW resistance into susceptible but highly adopted cultivars through marker-assisted backcross breeding and in conventional breeding programs.
Singh, M.,Sharma, K.,Dutta, N.,Singh, P.,Verma, A.K.,Mehra, U.R. Asian Australasian Association of Animal Productio 2007 Animal Bioscience Vol.20 No.10
A study was carried out to study the response of total purine derivatives (PD) excretion in urine to determine microbial N (MN) supply at four fixed levels of feed intake (namely 95, 80, 60 and 40% of voluntary intake). The crossbred (CB) calves were allocated according to a $4{\times}4$ Latin Square Design and fed wheat straw and concentrate (1:1). The rate of PD excretion (mmol/d) as a linear function of feed intake was 15.85/kg DMI and 20.12/kg DOMI. Based on the endogenous and PD excretion rates obtained in this study, a relationship between daily urinary PD excretion (Y, mmol) and daily microbial protein supply (X, mmol) was developed for crossbred calves as Y = 0.83X+0.296 kg $W^{0.75}$. The derived microbial N values using this equation differed (p<0.001) among the 4 groups and was the highest in L-95 followed by L-80, L-60 and L-40. The relationship between urinary nitrogen loss (Y, g/d) and DOMI (X, kg/d) was established as: Y = 6.038X+21.753 ($r^2$ = 0.663, p<0.01). When urinary excretion of PD (Y, mmol/d) was plotted against intake of DM and DOM (X, kg/d), the equations obtained were: Y = 7.1711X+8.674 ($r^2$ = 0.889, p<0.01) and Y = 12.434X+7.683 ($r^2$ = 0.896, p<0.01), respectively. The proportional contribution of allantoin and uric acid to total PD remained stable irrespective of level of feed intake. Similarly, urinary excretion of creatinine did not differ (p>0.05) between animals fed at different levels. The MN supply was the highest to animals at intake levels L-95, and decreased linearly with corresponding decrease in feed intake. However, the MN supply when expressed per kg DOMI remained statistically (p>0.05) similar irrespective of level of intake. The results revealed that the excretion of urinary purine derivatives were positively correlated with the level of feed intake as well as rumen microbial supply and thus it could be a good indicator for measuring the microbial protein supply and nutritional status of animals.
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.,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,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, 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>
PL and ESR of Gd3+ in LaMgAl11O19 phosphors
Singh, Vijay,Singh, N.,Pathak, M. S.,Watanabe, S.,Gundu Rao, T. K.,Singh, Pramod K.,Kwon, Young-Wan Springer-Verlag 2018 Journal of materials science Materials in electron Vol.29 No.6
<P>LaMgAl11O19 doped with different concentrations of gadolinium phosphors were synthesized by combustion and characterized using X-Ray diffraction to identify the crystalline phase. Photoluminescence studies on the sample showed emission peaks at 313 and 306 nm with lambda(exi) = 273 nm corresponding to the P-6 (J) -> S-8(7/2) transitions of Gd3+ ions. In phosphors with low dopant concentrations, dominant electron spin resonance lines are observed with g (eff) similar to 1.96, 1.98, 4.2, and 6.0. With increasing concentrations, the spectrum appears to be U-shaped, and main lines are seen at g (eff) similar to 1.98, 2.04, 2.8, 4.1 and 6.2. Distortions in the immediate environment of Gd3+ ions lead to relatively strong crystal fields and the appearance of lines in the low field region of the spectrum.</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>