Many impedance models have been proposed based on IS measurements
for various types of microstructures. One of them is the
internal barrier layer capacitor model or brick layer capacitor which
is usually found on structures of dielectric ceramic. The internal
barrier layer capacitor model is based on limited reoxidation of a
reduced composition and results in higher resistivity of the surface
layer than in a central portion [10]. A thinner reoxidized layer will
produce larger dielectric ceramic permittivity [11,12]. A modified
model structure is illustrated in Fig. 1(a). The capacitance, Ci of an