The Core-Shell Grain Resistance in the Reduced La-Doped (Ba, Sr)TiO₃ Ceramics

Abstract

Based on the oxygen-vacancy diffusion, a core-shell model of grain resistance is proposed, for the reduced La-doped (Ba, Sr)TiO3 ceramics, to describe the charge-carrier distribution. Complex impedance analysis is adopted to determine the grain resistance and grain boundary resistance. After sintering at 1400°C in reducing atmosphere, the low grain resistance is attributed to the effective electron compensation in the grain core, while the higher grain boundary resistance is thought to be due to the lower charge-carrier concentration in the grain shell. In addition, reoxidation leads to further decrease of charge-carrier concentration on the grain shell by diffusing inward to the grain core.