Studies on room temperature multiferroic properties of xBi_0.5Na_0.5TiO₃-(1-x)NiFe₂O₄ ceramics

Multiferroic ceramics xBi_0.5Na_0.5TiO₃-(1-x)NiFe₂O₄ (x = 0–1) have been prepared by a sol–gel method. Crystal structures were investigated by X-ray diffraction. The results show the samples are pure phases and increasing Bi_0.5Na_0.5TiO₃ content induces a gradual phase transformation from spinel to perovskite structure. Scanning electron microscopy micrographs also present the size and structure of the samples. Results from energy dispersive spectrometer confirm the stoichiometry of the compound. Both of the data are proved to agree with the results of X-ray diffraction. All of the samples display the evident ferromagnetic properties at 300 K and the saturation magnetization almost linearly varies with the increasing of x. The room temperature polarization-electric field loops were examined. Compared with pure NiFe₂O₄, superior ferroelectric properties are obtained with increasing maximum of polarization as the content of Bi_0.5Na_0.5TiO₃ increases. Dielectric properties were also studied. The dielectric constant is proved to increase as Bi_0.5Na_0.5TiO₃ content increases at room temperature and the dielectric loss decreases as Bi_0.5Na_0.5TiO₃ doped in NiFe₂O₄. In addition, some of samples exhibit the effect of magnetoelectric coupling.