Dielectric and impedance spectroscopy of BiFeO3-NaTaO3 multiferroics

Tailoring of physical properties of multiferroic BiFeO3 was carried out by introducing NaTaO3 ferroelectric to form (Bi1−x, Nax) (Fe1−x, Tax) O3 (x=0.0, 0.1, 0.2 and 0.3) solid solutions. The formation of the desired materials was confirmed by the X-ray diffractions analysis. The surface texture of the prepared materials, recorded by scanning electron microscope (SEM), exhibits a uniform grain distribution with few small voids suggesting the formation of high-density pellet samples. The impedance and dielectric properties of the materials were investigated for different concentrations (x) of NaTaO3 as a function of temperature and frequency. The relative dielectric constant and loss tangent decrease with increase in NaTaO3 concentration in the system. The grain and grain boundary contributions in the resistive and capacitive components of the samples were estimated using the complex impedance spectroscopy technique. The value of activation energy due to both grain and grain boundary is nearly same, but increases with an increase in composition (x). The nature of variation of dc conductivity confirms the Arrhenius-behavior of the materials. Study of frequency dependence of ac conductivity suggests that the material obeys Jonscher׳s universal power law, and the presence of ionic conductivity is observed.