Defect Structure in Undoped and Donor-Doped Polycrystalline Sr₂Bi₄Ti₅O₁₈

Abstract

An investigation on the ferroelectric and dielectric properties of donor-doped (vanadium, niobium) Sr₂Bi₄Ti₅O₁₈ ceramics was presented. Compared with the undoped ceramics all the donor-doped ceramics had obviously increased 2P _r . Three obvious peaks (P₁, P₂, P₃) on the dielectric loss curve D(T) were observed. One peak which was just a few degrees below the Curie point and ascribed to viscous motion of domain walls declined drastically with vanadium doping. And the decline may result from the increase in grain size, which resulted in a large 2P _r . With niobium doping the relaxation peaks P₁ and P₂ related to point defects declined gradually. Therefore, the increase in 2P _r of Sr₂Bi₄Ti₅O₁₈ upon niobium doping might relate to the significant weakening of defect pinning.

Keywords:

• Sr₂Bi₄Ti₅O₁₈
• donor doping
• remnant polarization
• dielectric loss
• point defect

ACKNOWLEDGE

The authors acknowledge the financial support by the National Natural Science Foundation of China (Grant No. 10274066).