Multiferroic behaviors of Co-doped Bi4NdTi3FeO15 ceramics

By using a multicalcination procedure, Co-doped Bi₄NdTi₃Fe${}_{1?x}$Co_xO₁₅ ($x=0.1,0.3,0.5\text{ and }0.7$) (Co_x) ceramics were synthesized. The samples showed a single-phase (SP) Aurivillius structure containing four perovskite layers. Plate-like morphology of the grains which is related to the layered perovskite structure of the samples was clearly observed by SEM. The multiferroic properties of the samples at room temperature (RT) were demonstrated by dielectric, ferroelectric and magnetic measurements. With x ranging from 0.1 to 0.7, all the samples show RT multiferroic properties although there is no obvious regularity between the Co content and the multiferroic property. Very interestingly, Co_0.3 sample exhibits the optimum RT magnetic property, which can be attributed to the inclination of occupying the inner octahedra center for doped Co ions and the nearly 1:1 ratio of Fe and Co ions in the inner octahedra. The present work offers new insight into the compositional design of promising lead-free RT multiferroic materials.