Complex impedance analysis of doped barium titanates

Abstract

BaTiO₃ ceramics doped with Nb⁵⁺ or Fe³⁺ ions were prepared by the conventional solid state sintering process, so as to investigate the effect of the type and amount of dopant on the complex impedance patterns of doped barium titanates. It was found that 0.3 mol% Nb-doped samples showed PTCR behavior with overlapping impedance arcs pertaining to grain and grain boundaries. On the other hand, complex impedance measurements always resulted in single arc or semicircle for 1 ∼ 4 mol% Nb-doped samples and for 0.1 ∼ 2 mol% Fe-doped samples, regardless of the amount of impurities and temperature. This result could be attributed to the grain boundary impedance for both Nb and Fe-doped samples.