Arti Yadav

ESR of vanadyl ions in borate glasses

Electron spin resonance (ESR) of VO 2+ in Li 2 O·RO·B 2 O 3 (where R = Ba, Ca and Mg) glasses have been studied. Spin Hamiltonian parameters, the dipolar hyperfine coupling parameter, and the Fermi contact interaction parameter have been calculated. It is observed that with a decrease in B 2 O 3 mol% there is an improvement in the octahedral symmetry of the V 4+ site. The theoretical value of optical basicity, Λ th , of these glasses has also been calculated. It is found that at constant mol% of Li 2 O there is a decreasc in A ∥ , A ⊥ and Δ g ∥ /Δ g ⊥ and an increase in P with increase in the value of Λ th , whereas at constant mol% of B 2 O 3 by varying modifier contents the spin Hamiltonian parameters are independent of Λ th .

EPR and impedance spectroscopic investigations on lithium bismuth borate glasses containing nickel and vanadium ions.

Glasses having composition 7NiO∙23Li2O∙20Bi2O3∙50B2O3, 7V2O5∙23Li2O∙20Bi2O3∙50B2O3 and x(2NiO∙V2O5)∙(30-x)Li2O∙50B2O3∙20Bi2O3 (with x=0, 2, 5, 7 & 10 mol%) prepared through melt-quench route are explored by analyzing density, impedance spectroscopy and electron paramagnetic resonance (EPR). It is found that both density and molar volume increase with an increase in substitution of 2NiO∙V2O5 in the base glass matrix. Different dielectric parameters viz. dielectric loss (ε), electrical modulus (M), loss tangent (tanδ) etc. are evaluated and their variations with frequency and temperature are analyzed which reveals that these glasses exhibit a non-Debye relaxation behavior. A phenomenal description of the capacitive behavior is obtained by considering the circuitry as a parallel combination of bulk resistance (Rb) and constant phase element (CPE). The conduction mechanism is found to follow Quantum Mechanical Tunneling (QMT) model. Spin Hamiltonian Parameters (SHPs) and covalency rates are calculated from the EPR spectra of vanadyl ion. The observed EPR spectra confirmed that V(4+) ion exists as vanadyl ion in the octahedral coordination with tetragonal compression.

Electron spin resonance of VO2+ and Cu2+ in lithium borate glasses

Etude des spectres RPE de VO 2+ et Cu 2+ dans des verres Li 2 O-B 2 O 3 prepares a differentes temperatures de fonte et avec un dopage simple ou mixte par les ions cu 2+ et VO 2+

Optical and thermal investigations on vanadyl doped zinc lithium borate glasses

Abstract Using standard melt-quench technique, transition metal oxide (2 mol% of V2O5) doped glasses having composition xZnO·(30 − x)Li2O·70B2O3 (x = 0, 2, 5, 7 and 10) are prepared. The density (D) is measured using buoyancy and found to be lying between 2.21 and 2.45 g/cm3 with an increasing trend on substituting ZnO contents in place of Li2O. The theoretical optical basicity (Λth) is calculated and found to increase with increasing inclusion of ZnO indicating an increase in the ionic character. The molar refraction (Rm), refractive index (nr) and molar polarizability (αm) are calculated and explained on the basis of structural changes. The optical absorption spectra have been used to evaluate the values of optical band gap (Eopt) and band tailing parameter (B). It is observed that Eopt decreases with the increasing contents of ZnO in base glass matrix. The decrease in Eopt is an evidence of enhancement in the number of non-bridging oxygen atoms (NBOs) thereby increasing the four-coordinated boron atoms. The as-quenched samples in bulk form are subjected to differential thermal analysis (DTA) to assess the glass transition temperature (Tg), which is 476 °C for pure lithium borate glass. The variations suggest that the structure is being modified by the substitution of ZnO.

ESR of vanadyl ions in borate glasses A. YADAV, V. P. SETH

The electron spin resonance (ESR) of VO2+ in Li2O-RO-B2O3 (where R = Sr, Zn) glasses hasbeen studied. Spin Hamiltonian parametersg\tT,g\t],A\tT andA\t], dipolar hyperfine coupling parameterP and Fermi contact interaction parameter K have been calculated. It is found that with a decrease in the percentage of B2O3 there is an improvement in the octahedral symmetry of the V4+ site. The theoretical optical basicity Ath, of the glasses has also been calculated.