Santhan Kumar

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Vasavi College of Engineering , Hyderabad, India

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SATISH KUMAR

Deenbandhu Chhotu Ram University of Science and Technology

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Deenbandhu Chhotu Ram University of Science and Technology

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Papers by Santhan Kumar

AN ESR AND OPTICAL STUDY OF VANADIUM DOPED K2O-CdO-B2O3 – SiO2 (KCdBSi) GLASSES

Glasses of the 20K2O 5CdO 60B2O3 -15SiO2 and (20-x) K2O 5CdO 60B2O3 15SiO2 – xV2O5 (where x=0.1to... more Glasses of the 20K2O 5CdO 60B2O3 -15SiO2 and (20-x) K2O 5CdO 60B2O3 15SiO2 – xV2O5 (where x=0.1to 0.5mol %) KCdBSi systems were prepared by melt quenching technique. Optical and structural properties of undoped glass, and glasses doped with VO 2+ ions were examined. Their structural properties were determined with XRD, Fourier Transform Infrared (FTIR) and Electron Paramagnetic Resonance spectra (ESR) and Optical absorption spectra. Optical band gaps of glass samples were determined for direct and indirect transitions from the absorption spectra. Through the fundamental Ultra Violet absorption edges of the glasses, the Optical band gap energies and Urbach energies were evaluated. The ESR spectra of all the glass samples exhibit resonance signals characteristic of VO 2+ ions. The values of Spin-Hamiltonian parameters indicated that the VO 2+ ion in KCdBSi glasses were present in octahedral sites with tetrahedral compression and belong to C4v symmetry. Spin Hamiltonian parameters ‘g’ ...

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Santhan AMR paper

Investigations on spectral features of tungsten ions in sodium lead alumino borate glass system

Journal of Physics and Chemistry of Solids, 2015

ABSTRACT Na2O–PbO–Al2O3–B2O3 (NPAB) glasses mixed with different concentrations of WO3 (ranging f... more ABSTRACT Na2O–PbO–Al2O3–B2O3 (NPAB) glasses mixed with different concentrations of WO3 (ranging from 0 to 2.5 mol%) are synthesized by conventional melt quenching method. The samples are characterized by X-ray diffraction (XRD), optical absorption, Electron paramagnetic resonance (EPR) and Fourier transform infrared (FT-IR) spectroscopic techniques. Glass formation is confirmed by X-ray diffraction spectra. The optical absorption spectra of these glasses exhibited a predominant broad band peak at about 850–870 nm is identified due to dxy–dx2−y2 transition of W5+ ions. From the optical absorption spectral data, optical band gap (Eopt) and Urbach energy (ΔE) are evaluated. From EPR spectra the strength of the signal is increased and hyperfine splitting is resolved with increasing concentration of WO3 in the glass matrix. The FT-IR spectral studies have pointed out the existence of conventional BO3, BO4, B–O–B, PbO4, WO4 and WO6 structural units of these glasses. Various physical properties and optical basicity are also evaluated with respect to the concentration of WO3 ions.

Spectral Studies of Vanadyl-Doped Cadmium–Strontium Borosilicate Glass System

Applied Magnetic Resonance, 2012

ABSTRACT Glasses with composition CdO–(20-x) SrO–B 2 O 3 –SiO 2 –x V 2 O 5 (CdSBSi) (x = 0.5, 1, ... more ABSTRACT Glasses with composition CdO–(20-x) SrO–B 2 O 3 –SiO 2 –x V 2 O 5 (CdSBSi) (x = 0.5, 1, 1.5, 2, 2.5 mol%) were prepared by melt quenching tech-nique. The amorphous nature of prepared glasses is confirmed by X-ray diffraction. Optical absorption spectra, electron paramagnetic resonance (EPR) and Fourier transform infrared (FTIR) measurements were also carried out for the prepared glass samples. The optical band gap energy (E opt) and Urbach energy (DE) were calcu-lated from their ultraviolet edges. The theoretical values of optical basicity (K th) of glasses have been evaluated. The optical absorption spectrum exhibits two band characteristic of VO 2? ions in tetragonally distorted octahedral site symmetry. The two bands have been assigned to the transitions 2 B 2 ? 2 B 1 and 2 B 2 ? 2 E in the decreasing order of energy. The spin–Hamiltonian parameters (g and A), bonding parameters (b* 2 and e Ã2 p), Fermi contact interaction parameter (K) have been eval-uated from the EPR spectra. The VO 2? site symmetry is ascribed to a tetragonally (C 4v) distorted octahedron. FTIR spectra of these glasses were analyzed in order to identify the contribution of each component to the local structure. The physical properties of these glasses were also evaluated.

EPR, optical and physical properties of chromium ions in CdO–SrO–B2O3–SiO2 (CdSBSi) glasses

Optical Materials, 2013

Chromium ions doped 10Cd O-(20Àx) SrO-50B 2 O 3-20SiO 2 (x = 0.5, 1.0, 1.5, 2.0, 2.5 mol%) (CdSBS... more Chromium ions doped 10Cd O-(20Àx) SrO-50B 2 O 3-20SiO 2 (x = 0.5, 1.0, 1.5, 2.0, 2.5 mol%) (CdSBSi) glasses have been studied by using Electron Paramagne tic Resonance (EPR) and optical absorption techniques at room temperature. Powder XRD pattern of all the samples confirms amorphous nature of the glass. The low field spectral line of the EPR spectrum of chromium ions in CdSBSi glass is attributed to isolated Cr 3+ ions and the high field spectral line is assigned for exchange of coupled pairs Cr 3+ ions in all these glasses. The optical absorption spectra of Cr 3+ ions in these glasses shows single broad band characteristi c of Cr 3+ ions in near octahedral symmetry. From this optical absorption spectral data the crystal field paramete r (Dq) is evaluated from ultraviolet absorption edges, the optical band gap and Urbach energies are evaluated. The results assert that the optical band gap energy values are depended quite sensitively on added chromium content. The FT-IR spectral investigations of chromium ion doped glasses exhibits characteristic vibratio ns of BO 3 units. Several physical parameters are also evaluated for these glasses with respect to the composition.

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Spectral investigations on VO 2+ ion doped in CaO–SrO–Na 2O–B 2O 3 glass systems

Journal of Non-crystalline Solids, 2011

Glasses of the (20 − x)CaO-xSrO-(20 − y)Na 2 O-60B 2 O 3 − y (CSNB) system with (5 ≤ x ≤ 15) mol%... more Glasses of the (20 − x)CaO-xSrO-(20 − y)Na 2 O-60B 2 O 3 − y (CSNB) system with (5 ≤ x ≤ 15) mol% and y = 0.1 mol% of V 2 O 5 were characterized by X-ray diffraction (XRD), EPR (Electron Paramagnetic Resonance), Optical absorption Spectra and FT-IR (Fourier transform Infrared Spectroscopy) studies. EPR spectra of all the glass samples exhibit resonance signals characterstic of VO 2+ ions. The values of spin-Hamiltonian parameters indicate that the VO 2+ ions in CSNB glasses were present in octahedral sites with tetragonal compression and belong to C 4v symmetry. Spin-Hamiltonian parameters 'g' and 'A' were evaluated. The Optical band energy (E opt ) and Urbach energy (ΔE) were calculated from their ultra violet edges. By correlating EPR and Optical data the molecular orbital coefficients have been evaluated. IR spectra of these glasses were analyzed in order to identify the contribution of each component to the local structure that determines the physical properties of these glasses.

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AN ESR AND OPTICAL STUDY OF VANADIUM DOPED K2O-CdO-B2O3 – SiO2 (KCdBSi) GLASSES

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Santhan AMR paper

Investigations on spectral features of tungsten ions in sodium lead alumino borate glass system

Journal of Physics and Chemistry of Solids, 2015