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# EPR and Optical Studies of Vanady Ions in Alkali Lead Borotellurite Glasses

Chakradhar, Sreekanth RP and Sivaramaiah, G and Rao, Lakshmana J and Gopal, NO (2005) EPR and Optical Studies of Vanady Ions in Alkali Lead Borotellurite Glasses. In: Modern Physics Letters B, 19 (13 & 1). pp. 643-653.

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## Abstract

Electron Paramagnetic Resonance (EPR) and optical absorption spectra of $VO^{2+}$ ions in different alkali lead borotellurite glasses have been studied. The spin-Hamiltonian parameters (g and A), bonding parameter $\beta_{2}.^{2}$ and Fermi contact interaction parameter k have been calculated. The values of spin-Hamiltonian parameters confirm that the vanadyl ions are present in the glasses as $VO^{2+}$ molecular ions in an octahedral site with a tetragonal compression. The number of spins (N) participating in resonance is calculated as a function of temperature (123-393 K) for 9 mol% of $VO^{2+}$ ions in lithium lead borotellurite glass sample. It is observed that N obeys the Boltzmann law. From EPR data, the paramagnetic susceptibility (\chi) is calculated at various temperatures and the Curie constant has been evaluated from $1/\chi$ graph. The optical absorption spectrum exhibits two bands characteristic of $VO^{2+}$ ions in tetragonal symmetry. The band gap $(E_{opt})$ and the Urbach energies $(\triangle E)$ have been determined from the ultraviolet absorption edges and are found to be dependant on the size of the alkali ion. The theoretical values of optical basicity $(A_{th})$ of these glasses have also been evaluated.

Item Type: Journal Article http://dx.doi.org/10.1142/S0217984905008... Copyright for this article belongs to World Scientific Alkali lead borotellurite glasses;EPR;optical absorption Division of Physical & Mathematical Sciences 26 Jul 2005 19 Sep 2010 04:19 http://eprints.iisc.ernet.in/id/eprint/3389

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