K. Siva Kumar

Spectroscopic investigations of Cu2+ in Li2O-Na2O-B2O3-Bi2O3 glasses

Pure and copper doped glasses with composition,xLi2O-(40-x)Na2O-50B2O3-10Bi2O3,have been prepared over the range 0 ≤x ≤ 40. The electron paramagnetic resonance (EPR) spectra of Cu2+ ions of these glasses have been recorded in the X-band at room temperature. Spin Hamiltonian parameters have been calculated. The molecular bonding coefficients, α2 and β2, have been calculated by recording the optical absorption spectra in the wavelength range 200–1200 nm. It has been observed that the site symmetry around Cu2+ ions is tetragonally distorted octahedral. The density and glass transition temperature variation with alkali content shows non-linear behaviour. The IR studies show that the glassy system contains BO3 and BO4 units in the disordered manner.

Optical absorption and electron spin resonance studies of Cu2+ in Li2O-Na2O-B2O3-As2O3 glasses

The local structure around Cu2+ ion has been examined by means of electron spin resonance and optical absorption measurements in xLi2O-(40-x)Na2O-50B2O3-10As2O3 glasses. The site symmetry around Cu2+ ions is tetragonally distorted octahedral. The ground state of Cu2+ isdx2−y2.The glass exhibited broad absorption band near infrared region and small absorption band around 548 nm, which was assigned to the2B1g →2Egtransition.

Transport Properties of (NH4)2 CuCl4.2H2O Low Dimensional Single Crystals

The X-ray diffraction and Infrared (IR) spectral studies of (NH 4 ) 2 CuCl 4 .2H 2 O single crystals reveals that these crystals contains tetragonal crystal structure with the unit cell dimensions of a = 7.58A, c = 7.95A, z= 2, β =90° and two water molecules in the unit cell. The temperature dependence of thermally stimulated depolarization current (TSDC) and dc electrical conductivity (a) studies of this two-dimensional (NH 4 ) 2 CuCl 4 .2H 2 O single crystal have been carried out in 77K-300K temperature region. The TSDC thermograph shows only one sharp peak at 248K with a peak current of 130nA, which is attributed to the Maxwell-Wagner peak. The activation energy (U), relaxation time (τ) are calculated as 0.78eV and 3.44×10 -15 s respectively. Dc electrical conductivity studies of these crystals show a first order phase transition at about 248K.

Small angle X-ray scattering studies of poly-(3′-octyl-2, 2′-terthiophene) and poly-(3-octyl-2,2′; 5′2″-terthiophene) thin films

Abstract Small angle X-ray scattering (SAXS) experimental technique is applied in obtaining the macromolecular parameters (radius of gyration R g , radius R , specific surface area S s and surface morphology) of two polythiophene derivative (poly-(3′-octyl-2, 2′-terthiophene) (POTT) and poly-(3-octyl-2,2′; 5′2ʺ-terthiophene) (POTT)) thin films. Nanosized thin films of these two polymers were prepared on glass substrate with thickness around 3.5 μm by spin coating. SAXS experiments are performed with an 18-kW rotating anode X-ray generator equipped with a Cu target. A two-dimensional proportional counter is employed to detect the scattered X-rays intensity. Analysis of SAXS data using the Guinier approximation, the radius of gyration of POTT and PTOTT particles are determined as 10.28 and 11.05 A, respectively. Similarly, the radii of these samples are determined as 13.28 and 14.14 A. Porod approximation is used to find specific surface area of POTT and PTOTT nanostructured polymeric thin films, and they are determined as 4.78×10 8 and 5.38×10 8 cm −1 , respectively. The surface fractal dimensions of POTT and PTOTT films are determined as 2.81 and 2.65, respectively.

Optical properties of amorphous Li2O–WO3–B2O3 thin films deposited by electron beam evaporation

Abstract Thickness dependencies of the optical properties of as-deposited amorphous 30Li2O–10WO3–60B2O3 thin films prepared by electron beam evaporation on glass substrates at a base pressure of 9 × 10−7 Torr were studied. Glancing angle X-ray diffraction studies were performed to confirm the amorphous nature of the prepared films. The absorption coefficient α (and therefore the extinction coefficient k) was determined from the reflectance and transmission spectra in the strong absorption region. The dispersion of the refractive index is discussed in terms of the single-oscillator Wemple–DiDomenico model. The optical constants, such as optical band gap, Urbach energy, the average excitation energy Eo and the dispersion energy Ed, of the thin films were determined. The optical data revealed the existence of allowed indirect transitions.

Transport properties of Mg2+ ion doped α-Cu(COOH)2 single crystal

The temperature dependence of dc electrical conductivity (σ) and thermally stimulated depolarization currents (TSDC) of a new low-dimensional MgxCu(COOH)2 single crystals have been studied in 77–300 K temperature range. The electrical conductivity in this crystal is found to be mainly due to non adiabatic hopping mechanism, and the crystal undergoes a Peierls transition at about 208 K. The TSDC thermograph shows only one peak at 183 K in the pure (i.e. x=0 mol%) crystal which is attributed to the detrapping of holes, while three peaks in the Mg2+ ion doped (i.e. x=1 and 2 mol%) crystals. These three peaks are assigned as one due to ion vacancy (I-V) dipole redistribution, the second due to detrapping of charge carriers (holes), and the third is due to Maxwell–Wagner effect.

Ionic transport and battery characterization studies in (30-x)Na2O xNaF60B2O310Tl2O glasses

Abstract The results from measurements of the d.c. electrical conductivity of the Na 2 ONaFB 2 O 3 Tl 2 O glass system and the transference number are reported. Electrochemical cells with the configuration Na/(30Na 2 O60B 2 O 3 10Tl 2 O)/(graphite + iodine + electrolyte) have been fabricated and the discharge characteristics examined. The open-circuit voltage and the short-circuit current (maximum) are 2.27 V and 2.19 mA, respectively. Several other cell parameters are reported.

Physical and optical studies on Li2O-Na2O-WO3-B2O3 glasses

Glasses with composition xLi2O-(30-x)Na2O-10WO3-60B2O3 (where x=0, 5, 10, 15, 20, 25 and 30 mol%) have been prepared using the melt quenching technique. In the present work, the mixed alkali effect (MAE) has been investigated in the above glass system through density and optical studies. The density of the present gasses varies non-linearly, the exhibiting the mixed alkali effect. From the optical absorption studies, the values of direct optical band gap, indirect optical band gap energy (Eo) and Urbach energy(ΔE) have been evaluated. The values of E0 and ΔE vary non-linearly with composition parameter, showing the mixed alkali effect.

Magnetic Resosnance Studies of Nano Phase Conducting Polyaniline

Polyaniline (PANI) was synthesized in Emaraldine form by in situ chemical oxidation method by using Ammonium perdisulphate as oxidizing agent. The XRD pattern indicates that PANI is a semi crystalline solid with d-spacing 4.801 and 4.358 Ǻ. The SEM results show that the particle size lies as an average of 80 nm and length 550 nm. Similarly the UV-Visible spectra of this polymer indicate two absorption bands at around 320 nm and 640 nm. These absorption bands are attributed to the transitions of π → π* and Benzenoid to Quinoid respectively. The FT-IR spectrum of PANI shows strong bands at 3,442, 2,925, 1,598, 1,494, 1,453, 1,176, 1,112 and 744 cm−1 respectively. 1H NMR spectrum shows 6 peaks with chemical shifts δ = 7.452, 7.468, 7.505, 7.525, 7.604, 7.638 ppm. The lower three peaks at (δ = 7.452, 7.468, 7.505 ppm) are attributed to the protons related to the 14N nucleus. These spectral lines intensity ratio lies as 1:1:1. Another three peaks at (δ = 7.525, 7.604, 7.638 ppm) are attributed to the three protons, which are present at CH Benzenoid, NH, CH at Quinoid. The intensity ratio of these spectral lines is 1:2:1. The room temperature ESR spectrum of PANI Emeraldine salt shows an unresolved peak with lande’s g factor 2.010 due to polarons.

SPECTROSCOPIC AND TRANSPORT PROPERTIES OF A NEW LOW. DIMENSIONAL SINGLE CRYSTAL

Abstract Spectroscopic properties (IR, EPR & Optical absorption), DC electrical conductivity (77K-300K range) of SrCu(HCOO)4 single crystal have been studied. The IR spectrum gives five strong bands at 3250, 1608, 1331, 779 and 667 cm−1. These bands are attributed to the stretching and bending vibrations of formate ion atoms. EPR results indicate that the Jahn-Teller active copper(II) ion is present in tetragonal elongated octahedral crystal field. Optical absorption in UV, Visible and in near Infrared regions shows ten absorption bands. The absorption bands in the UV and Visible regions are attributed to the charge transfer and cubic field splitting respectively. The eight absorption bands in the near infrared region are assigned to the d-d transitions of copper(II) ion, the Hubbard energy gaps of the crystal and to the Fermi energy gap of the crystal. Finally the weak absorptions are attributed to the linear combinations of IR bands, DC electrical conductivity of this crystal is assigned to the hopping ...