Synthesis of Ni-substituted Bi7Fe3Ti3O21 ceramics and their superior room temperature multiferroic properties

Layer-structured bismuth complex oxides Bi7Fe3−xNixTi3O21 (0 ≤ x ≤ 2) (BFNT) were synthesized using a low-temperature combustion synthesis method. X-ray diffraction patterns and high-resolution transmission electron microscopy analysis indicated that the samples presented a six-layer Aurivillius structure. Substituting Fe sites by Ni ions inside the lattice was found to be effective in enhancing the multiferroic properties at or above the room-temperature. The sample with a composition of x = 1 exhibited a large remnant magnetization (2Mr = 1.32 emu g−1) that is about five hundred times higher than that in un-substituted Bi7Fe3Ti3O21 ceramics. The work is an important step in the effort to find a single phase and a fully functioning multiferroic material.