Aging of Dielectric Properties in Na_0.5Bi_0.5TiO₃ Ceramics

Abstract

Aging of Na _{0.5 + x} Bi _{0.5 − x} TiO _{3 − x} (x = 0, 0.02) ceramics is studied by dielectric measurements. The time dependence of the dielectric property is well fitted by the stretched exponential function. The observed aging temperature dependences are different between Na _0.52 Bi _0.48 TiO _2.98 and Na _0.5 Bi _0.5 TiO ₃ in relation with the concentration of oxygen vacancies. The aging temperature dependences of the relaxation intensity and the relaxation time in Na _0.52 Bi _0.48 TiO _2.98 (which contains more oxygen vacancies) is consistent with the result of Monte-Carlo simulation which is based on the relaxation of defect dipoles in relaxor ferroelectrics. It is found that the oxygen vacancies are mainly responsible for the defect dipole. The aging behavior can be explained on the basis of the size of defect-dipole and its distribution.

Keywords:

• Ferroelectrics
• aging
• dielectric
• defect dipole
• relaxation
• NBT

PACS numbers:

• 61.72.J-
• 77.22.-d
• 77.22.Gm
• 77.84.Dy