Grain boundary defect compensation in Ti-doped BaFe0.5Nb0.5O3 ceramics

Giant dielectric ceramics Ba(Nb0.5Fe0.5-xTix)O3 (BNFT) have been fabricated by a conventional solid-state reaction. According to X-ray diffraction analysis, the crystal structure of these ceramics can be described by the cubic centrosymmetric with Pm-3m space group. The real part (ε’) of dielectric permittivity and dielectric loss (tanδ) of the BNFT ceramics was measured in a frequency range from 40 Hz to 100 MHz at room temperature. The (ε’) of all these samples displays a high value (~6500) and a small frequency-dependence from 1 kHz to 1 MHz. We have established a link between conductivity activation energy and defect compensation at grain boundaries. The Ti4+-doped Ba(Nb0.5Fe0.5)O3 as a donor makes a great influence on the grain boundary behavior, which restricts the migration of oxygen vacancy and depresses dielectric loss factor for Ba(Nb0.5Fe0.5)O3 ceramics.