Dielectric relaxations in Ba(Fe_(1/2)Ta_(1/2))O_3 giant dielectric constant ceramics

摘要

Dielectric relaxations of Ba(Fe_(1/2)Ta_(1/2))O_3 ceramics were investigated and discussed over a broad temperature and frequency range. Two dielectric relaxations following Arrhenius law were observed at 153-382 and 440-623 K, where there was a giant dielectric constant step between them. The frequency dependent rapid drop of dielectric constant at 153-382 K was nearly a Debye relaxation with the intrinsic nature, while the high temperature dielectric relaxation with an extremely high dielectric constant peak and very strong frequency dispersion was attributed to the defect ordering but not a typical relaxor ferroelectric behavior. The O_2 annealing almost completely suppressed the dielectric peak and subsequently extended the giant dielectric step, while the low temperature dielectric relaxation and the magnitude of such step were not obviously affected.