Effects of Ni doping on ferroelectric and ferromagnetic properties of Bi0.75Ba0.25FeO3

Variants of Ni-added Bi0.75Ba0.25FeO3 (BBFO) multiferroic ceramic were prepared by the sol–gel method. The first variation line was the synthesis of Bi0.75Ba0.25Fe1−xNixO3 (x=0, 0.025) solid solutions. The second variation was the preparation of BBFO impregnated with nickel oxide. Synthesized materials were characterized by x-ray diffraction (XRD) and scanning electron microscopy (SEM). Ferroelectric and ferromagnetic measurements were conducted as well. XRD data suggest the coexistence of a rhombohedral and a tetragonal phase when Ba2+ and Ni2+ cation substitutions are present. Ni acts as an inhibitor of grain growth and coalescence. After sintering, it reduces the average size from 88 nm to 67 nm. Furthermore, the presence of the Ni2+ cation in the Bi0.75Ba0.25Fe0.975Ni0.025O3 octahedral position increases the saturation magnetization and suppresses the leakage current, which dampens the ferroelectric character of the non-doped perovskite family of BBFO. The Ni-doped BBFO ceramic achieves an interesting compromise between ferromagnetic and ferroelectric properties.