Influence of cobalt ions on dielectric features and a.c. conductivity of lead bismuth silicate glasses

Abstract

This investigation is devoted to study the influence of CoO concentration on dielectric characteristics of a heavy metal oxide glass system viz., lead bismuth silicate. The auxiliary spectroscopic studies have indicated progressive increase of the fraction of tetrahedral (Td) divalent cobalt ions in the glass structure as the concentration of CoO is gradually raised. Dielectric parameters measured in the wide range of frequencies and temperatures showed a lowering trend with CoO content; such result is attributed to the growing presence of Co2+ (Td) ions that participate in the glass structure that would obstruct the migration of charge carriers towards electrodes. Electric moduli variations have exhibited dipolar relaxation effects. Co2+ (Oh) and Bi3+ ions were predicted to be responsible for these effects. A. c. conductivity and (N(EF)) the concentration of disordered states exhibited decreasing trend, whereas activation energy for a.c. conduction showed increasing trend with CoO content. Impedance plots drawn as a function of CoO concentration suggested the increasing impedance of the glasses. The quantitative analysis of results of dielectric studies suggested that Co ions prevailingly took part in the glass network in Td locations, facilitated the growing polymerization of the glass structure and thereby increased stiffness of the glass network against the applied electrical filed or increased the electrical insulating strength of the glasses. Finally, it is concluded that these glasses may be considered for applications as transparent electrical shielding sheets in display panels.