Giant dielectric response and relaxor behaviors induced by charge and defect ordering in Sr(Fe1/2Nb1/2)O3 ceramics

Dielectric spectra of Sr(Fe1/2Nb1/2)O-3 ceramics were characterized in wide temperature (123-623 K) and frequency (100 Hz-1 MHz) ranges. Two dielectric relaxations with strong frequency dispersion and following the Arrhenius law were detected in low and high temperature ranges, respectively, and between them there was a giant dielectric constant step. The high temperature relaxorlike dielectric peak could be almost completely removed by annealing in O-2, and it should be assigned to be a defect ordering induced relaxor behavior, while the low temperature dielectric relaxation was proposed to stem from the electronic ferroelectricity. Moreover, it was speculated that the giant dielectric constant step resulted from the competing balance between the low and high temperature dielectric relaxations. (C) 2007 American Institute of Physics.