Syed Rahman

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.

FT-IR and Raman spectroscopic studies of ZnF2–ZnO–As2O3–TeO2 glasses

Abstract The effect of fluorine substitution on the spectral properties of the xZnF2–(20-x)ZnO–40As2O3–40TeO2 (x = 0, 4, 8, 12, 16 and 20 mol%) glass system was investigated by FTIR and Raman spectroscopies. The results demonstrate that TeO4 and TeO3 were among the primary structural units in the investigated glasses in addition to As2O3 pyramids and ZnO4 structural units. The addition of fluorine results in the reduction of Te–O–Te linkage due to a gradual transformation of trigonal bipyramidal TeO4 through TeO3+1 to trigonal pyramidal TeO3, which decreases the connectivity of the tellurite glass former network. The theoretical optical basicity of the studied glasses decreases with increasing ZnF2 content.

Calorimetric measurements on Ge-Bi-Se-Te glasses

On presente les resultats de mesures calorimetriques sur des verres Ge 2 0 Bi x Se 70-x Te 10 (x-7, 9, 11 et 13). On etudie les variations de la temperature de transition vitreuse, de la temperature de cristallisation en fonction de la teneur en bismuth

Role of ZnO in Dc Electrical Conductivity of Lithium Bismuthate Glasses

Glasses of various compositions belonging to the Bi2O3-B2O3-ZnO-Li2O quaternary system were prepared using melt quench technique. Dc electric measurements were done on the samples, and activation energies are determined. Arrhenius plots showed straight line behaviour. It is observed that the conductivity of the samples increased with temperature and also with Li2O content, whereas the activation energy decreased with Li2O content. The isothermal plots for constant ZnO and constant Bi2O3 glasses revealed that the conduction in these glasses is due to lithium ions only. The isothermal plots for constant lithium containing glasses varied nonlinearly with two maxima, which is attributed to mixed former effect. The variation is explained based on Anderson-Stuart model.

EPR and Optical Absorption Spectral Investigations of Cu2

Electron paramagnetic resonance and optical absorption studies of Bi2O3-ZnO-B2O3-Li2O glasses were made by introducing Cu2

Spectroscopic and Physical Properties of Bi2O3-B2O3-ZnO-Li2O Glasses

Bismuth glasses containing ZnO and Li2O were prepared by conventional melt-quench technique. ZnO is gradually substituted by Li2O, and its effect on various physical, thermal, and electrical conduction properties was studied and analyzed. Raman studies revealed that these glasses are mainly made up of [BiO3] and [BiO6] units. The density decreases and molar volume increases with the incorporation of Li2O into these glasses. MDSC studies have been performed on these glasses to determine the glass transition temperature and other related thermal parameters such as change in the glass transition temperature (Δ𝑇𝑔) and specific heat capacity difference (Δ𝐶𝑝). These studies revealed that the glasses possess high 𝑇𝑔 values, and 𝑇𝑔 decreases with Li2O content. The trend of these properties is attributed to the changes in the glass network structure. Dc electrical conductivity revealed that the conductivity increases and activation energy decreases with Li2O content.

Electron paramagnetic resonance study of VO2+, Mn2+ and Cu2+ in oxyfluoroborate glasses

Abstract Electron paramagnetic resonance (EPR) studies have been performed on 20mol.%Li2O-10mol.%Li2F2-70mol.%B2O3 glass doped with vanadium, manganese and copper. In the presence of vanadium, a VO2+ group is observed with an anisotropic hyperfine structure. The EPR spectrum of Mn2+ exhibits resonances at g=1.956 and 4.468 and a shoulder at around 2.968. Cu2+ is located in a tetragonally elongated octahedral coordination. Its Jahn-Teller character gives rise also to an anisotropic hyperfine structure. The spin Hamiltonian parameters are evaluated. The effect of addition of fluorine on the spin Hamiltonian parameters is discussed.

Electronic switching in GeBiSeTe glasses

Abstract Thin Ge 20 Bi 70−x Te 10 (x=7,9,11 and 13) films were studied for their switching properties. It is shown that the switching characteristics can be varied by controlling the film thickness and concentration of bismuth. It was observed that films with x⩾9 exhibited electronic switching. The results were analysed on the basis of a chemically ordered network model (CONM), where the formation of a sufficient number of heteropolar bonds is favoured over the formation of homopolar bonds.

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.