Asian Research Thesis Index

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.

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