Studies of structural, dielectric, electrical and ferroelectric characteristics of BiFeO₃ and (Bi_0.5K_0.5)(Fe_0.5Ta_0.5)O₃

The polycrystalline samples of BiFeO₃ and (Bi_0.5K_0.5)(Fe_0.5Ta_0.5)O₃ were prepared using a solid-state reaction technique. Using room-temperature X-ray diffraction data the formation of a single-phase hexagonal crystal system of (Bi_0.5K_0.5)(Fe_0.5Ta_0.5)O₃ was confirmed. Scanning electron micrographs confirming the polycrystalline nature of the samples contain uniform grain distribution of unequal size. Temperature-frequency dependence of dielectric studies does not show any dielectric anomaly or phase transition in the materials in the studied temperature range. However, existence of hysteresis loop at room temperature has confirmed the known ferroelectricity of BiFeO₃ and (Bi_0.5Li_0.5)(Fe_0.5Ta_0.5)O₃. Analysis of complex impedance data has provided the amount of contributions of grain/grain boundary in the materials resistance. This analysis also shows that that the system has Negative temperature coefficient of resistance type behaviour. The electrical conductivity and relaxation characteristics of the system suggest the existence of thermally activated process, and their values suggest that the system has similar type of conductivity and relaxation species. The frequency dependence of the ac conductivity obeys Jonscher’s universal power law.