The dispersion in AC conductivity has been seen in wide
variety of disordered solids like, ion conducting glasses, amor-
phous semiconductors, ionic and electronic conducting polymers,
organic semiconductors, non-stiochiometric or highly defective
crystals, doped semi conductors, single crystals, etc. [1–5]. At low
frequencies, one observes a constant conductivity while at higher
frequencies the conductivity becomes strongly frequency depen-
dent. The generality of this behavior for many widely different
classes of materials was pointed out by Jonscher et al. [6].
Heavy metal oxide glasses (HMO) containing bismuth oxides
have received increased interest due to their manifold possible
applications [7–9]. These glasses were found to be efficient X-ray
absorbers and also considered for use in scintillation detectors for
high energy physics. The large polarizability and small field
strength of Bi
3þ in oxide glasses makes them suitable for optical
devices such as ultra fast all-optical switches, optical isolators,
optical Kerr shutter (OKS) and environmental guidelines. Despite
the fact that Bi2O3 is not a classical glass former, in the presence of
conventional glass formers (such as B2O3,SiO2, etc.) it may build a
glass network of [BiOn](n¼3, 6) pyramids [10]. Due to its dual role,
as modifier with [BiO6] octahedral and as glass former with [BiO3]
pyramidal units, bismuth ions may influence the electrical proper-
ties of glasses. The addition of Li, Mg, Zn, Fe oxides to these glasses
[11–13] results in large glass formation domain.