Structural, Optical, and Magnetic Properties of the New (1-x)Bi0.5Na0.5TiO3 + xMgCoO3-δ Solid Solution System

Abstract

A new (1-x)Bi0.5Na0.5TiO3 + xMgCoO3-δ solid solution system was synthesized using the simple sol–gel method. The structure that was investigated via X-ray diffraction and Raman scattering analysis indicated that the MgCoO3-δ materials were highly soluble into the host Bi0.5Na0.5TiO3 crystals. The random incorporation of Mg and Co cations into the host crystal of the Bi0.5Na0.5TiO3 materials reduced the optical band gap energy and induced a complex magnetic behavior as a function of MgCoO3−δ concentration solute in the host matrix. The optical band gap energy values decreased from 3.05 eV for pure Bi0.5Na0.5TiO3 materials to 2.22 eV with 9 mol% MgCoO3-δ solution for the Bi0.5Na0.5TiO3 compounds. A weak ferromagnetic property with strongly induced diamagnetism was obtained at room temperature for the pure Bi0.5Na0.5TiO3 materials, whereas ferromagnetic properties were observed for the MgCoO3-δ-modified Bi0.5Na0.5TiO3 compounds. The addition of paramagnetic and/or antiferromagnetic-like behavior was obtained for the MgCoO3-δ solid solution with over 5 mol% in the host Bi0.5Na0.5TiO3 materials. This work contributes to the current understanding of the interaction of transition metal cations in the host crystal ABO3 perovskite of lead-free ferroelectric materials due to the co-modification of A and B sites.