Abstract:
Two batches of polycrystalline materials; Bi 1-x Ba x FeO 3 and Ba 1-2x Bi 2x Fe 1-x Nb x O 3
have been synthesized by solid state reaction method. The structural studies have been
carried out by employing high resolution synchrotron X-Ray Diffraction (XRD), scanning
electron microscopy (SEM) and Mössbauer spectroscopy. The dielectric properties are
investigated by employing impedance spectroscopy. The DC electrical transport
properties have been investigated by considering different conduction mechanisms. The
magnetic properties have also been investigated at room temperature.
The XRD data of the two batches have indicated a structural transition from
rhombohedral to pseudo cubic symmetry at about 15% Ba substitution. The impurity
phases are suppressed in the cation doped samples. The leakage current density in the Ba
doped samples is reduced up to about four orders of magnitudes; however, the co-
substitution with Ba 2+ and Nb 5+ in the compensated ratio has greatly reduced the leakage
current up to about six order of magnitudes as compared to the undoped BiFeO 3 . The
oxygen vacancies are found to have the dominant role in the leakage current. The
overlapping large polaron tunneling (OLPT) and correlated barrier hopping (CBH) are
the governing models for lightly doped samples in low temperature region and heavily
doped samples at high temperatures, respectively. Although Nb doping is useful for the
enhancement of the electrical resistivity; yet it significantly degrades the ferromagnetism
appearing in the vicinity of Ba doping.
