Effects of bismuth doping on the dielectric properties of Ba(Fe0.5Nb0.5)O3 ceramic

The ferroelectric ceramic Ba1−xBix(Fe0.5Nb0.5)1−x/4O3 (BBFN) is synthesized by a solid-state reaction. It has a partially disordered perovskite structure and shows a maximum plateau of the dielectric permittivity depending upon the temperature. The X-ray diffraction of the sample ( x ≦ 0.06 ) at room temperature shows a monoclinic phase. When the doped contents of Bi are over 6 mole% the structure changes from monoclinic to tetragonal. The dielectric constant initially remains constant with increasing temperature up to a particular temperature T a , beyond which it increases rapidly. The temperature variations of the real and imaginary components of the dielectric permittivity show a broad maximum. The frequency dependence of the loss peaks is found to obey an Arrhenius law with activation energy of 0.155 eV. The Cole–Cole plot analysis of BBFN shows that the high dielectric constant is not grain responsive, but is a grain boundary effect as a typical barrier layer capacitor. All these observations show the dielectric relaxation properties of BBFN perovskites.