Correlating structure, dielectric and impedance studies with lanthanum-ion substitution in bismuth titanate

A correlated study involving structure analysis, temperature dependence of dielectric functions and the complex impedance spectroscopy analysis was carried out in lanthanum modified bismuth titanate (BT, Bi4−xLaxTi3O12; x = 0, 0.75) ceramics. A series addition of three RQ circuits has been shown to remarkably fit the complex impedance data for both x = 0 and 0.75 samples, which were attributed to crystalline layer, plate boundary and grain boundary microelements. Temperature dependence DC-conductance of these microelements has revealed that lanthanum-ion substitution is mainly taking place in the perovskite blocks, which also led to decrease in orthorhombic splitting. This site preferred substitution was also consistent with shift in the oxygen ion-jump relaxation peak in the temperature dependence of the dissipation factor study.