Electrical and magnetic characterization of Bi1 − xFexNbO4 ceramics.

Bi_{1 − x}Fe_xNbO₄ (x = 0.25, 0.50, and 0.75) samples were synthesized by the sol–gel method and its morphologic, structural, dielectric, and magnetic properties were studied. The structure was analyzed by X-ray diffraction and the morphology by scanning electron microscopy. The dielectric characterization that was performed using impedance spectroscopy, in the frequency range of 10²–10⁶ Hz, as a function of temperature, revealed that the dielectric constant and the dielectric losses increased with the iron content. The prepared materials presented relaxation processes, with the corresponding activation energies being calculated by fitting the experimental data to the Arrhenius model. The dependence of AC conductivity on frequency was found to satisfy Jonscher's universal power law at different temperatures. The conduction mechanisms are governed by two processes: correlated barrier hopping (CBH) and non-overlapping small polaron tunneling (NSPT). Magnetic susceptibility, for an applied magnetic field of 0.5 T, doubles when the iron concentration goes from 0.25 to 0.5 and doubles again when the iron concentration rises to 0.75. The increase in magnetization with the concentration of iron is also observed in the curves M vs. H at 7 K. The remaining magnetization and the coercive field do not exist for x = 0.25 (paramagnetic behavior); it is small for x = 0.5 and is already observed when x = 0.75. [ABSTRACT FROM AUTHOR]