Identification and comparison of peculiarities in physical properties of multiferroic morphotrophic phase boundary sintered BiFeO3-xPbTiO3 nano-ceramics

Abstract

In this paper a comprehensive study that includes structural, magnetic, ferroelectric, dielectric and electrical characterizations of as-prepared and quenched MPB 1-x(BiFeO3)-x(PbTiO3)(BF-xPT) solid solutions prepared by wet chemical method has been presented. Qualitative and quantitively structural analysis revealed coexistence of rhombohedral/monoclinic, tetragonal and orthorhombic phases. Sensitivity to the experimental variables such as composition, synthesis conditions, sintering temperature and particle size, confirms the existence of a complex energy phase diagram where minima associated with various polymorphs lies almost at same level for MPB compositions. Magnetic characterizations reveal the presence of three anomalies, i.e., originating from the Néel transition, iso-structural transition and ferroelectric phase transition. Second anomaly detected to be the most sensitive to the quenching. Enhancement of magnetic moment in quenched compositions is a manifestation of strong interaction between spins of Fe2+ ions with the pinned point defect dipoles. Interestingly, thermal quenching enhanced the ferroelectric properties by removing the domain wall pinning. Saturated ferroelectric loops were observed only for quenched samples which is a consequence of strong domain wall de-pinning. Low temperature dielectric relaxation has been observed while the high temperature dielectric data of as-prepared composition exhibited Maxwell-Wagner and iso-structural phase transition. In contrast, along with these two features, quenched samples showed additional Curie transition. Enhancement in large polaron hoping in the low frequency region for the quenched composition has been confirmed via frequency dependent profile of the ac conductivity. Low value of activation energy of charge carriers for quenched compositions indicates large polaron hoping characteristics in BF-xPT solid solution.