title: EPR and impedance spectroscopic investigations on lithium bismuth borate glasses containing nickel and vanadium ions.
abstract: 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.
authors.affiliation: Department of Physics, Deenbandhu Chhotu Ram University of Science and Technology, Murthal, Sonipat 131039, India.
authors.forename: Arti
authors.initials: A
authors.lastname: Yadav
authors.affiliation: Department of Physics, Deenbandhu Chhotu Ram University of Science and Technology, Murthal, Sonipat 131039, India. Electronic address: skhasa@yahoo.com.
authors.forename: Satish
authors.initials: S
authors.lastname: Khasa
authors.affiliation: Department of Physics, Deenbandhu Chhotu Ram University of Science and Technology, Murthal, Sonipat 131039, India.
authors.forename: Ashima
authors.initials: A
authors.lastname: Hooda
authors.affiliation: Department of Physics, Deenbandhu Chhotu Ram University of Science and Technology, Murthal, Sonipat 131039, India.
authors.forename: Manjeet S
authors.initials: MS
authors.lastname: Dahiya
authors.affiliation: Department of Applied Physics, Guru Jambheshwar University of Science and Technology, Hisar 125001, India.
authors.forename: Ashish
authors.initials: A
authors.lastname: Agarwal
authors.affiliation: Department of Physics, S R M University, Sonipat, Haryana 131029, India.
authors.forename: Prem
authors.initials: P
authors.lastname: Chand
keywords: AC conductivity; Dielectric constant; EPR; Glass; Nyquist diagram