Abstract
Ferroelectric and dielectric properties of niobium-doped Sr2Bi4Ti5O18 ceramics were investigated. Compared with the undoped ceramics, the niobium-doped ceramics exhibited obviously increased remnant polarization 2Pr, which is similar to the case of vanadium doping. However, the mechanisms of increasing of 2Pr by vanadium and niobium doping are quite different. In the case of Nb-doping, one relaxation peak P1 is found on the dielectric loss curves D(T) at 70 °C. The dependence of the peak on various annealing atmosphere indicates that the relaxation mechanism of the peak is related to oxygen vacancies. With niobium doping, the P1 peak declines gradually. These results suggest that the substitution of Ti4+ by a small amount of Nb5+ can result in the decreasing of the concentration of oxygen vacancies. Thus, the increase in 2Pr of Nb-doped Sr2Bi4Ti5O18 could be attributed to the significant weakening of defect pinning.
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