Room-temperature multiferroic enhancement in cobalt and iron co-doped Aurivillius ceramics via defect engineering strategy

Bi3.25Nd0.75Ti3-x(Fe0.50Co0.50)xO12 ceramics (BNdT-FCx) with 00.30 were synthesized using the solid-state reaction method. The structural analysis confirmed the presence of the orthorhombic Bi4Ti3O12 (BiT) phase, characterized by the space group B2cb. Rietveld refinement revealed pronounced octahedral distortions, particularly in the Ti(2)O6 octahedra, which became more prominent with increasing Co (Cobalt) and Fe (Iron) co-doping levels. Dielectric measurements over the 300-1000 K temperature range exhibited significant lowfrequency dielectric dispersion, attributed to increased localized charge carriers' contribution. Structural distortions strongly influenced the ferroelectric properties, specifically octahedral tilting and A-site ion displacement along the a-axis, which play a critical role in the polarization mechanism. The magnetic study indicated modest magnetic interactions in Nd-doped samples, whereas co-doping with Co3+/Fe3+ induced discernible ferromagnetic behavior, as evidenced by M-H hysteresis loops. Incorporating Co3+/Fe3+ co-dopants introduced oxygen vacancies, which correlated with a reduction in ferroelectric performance, likely due to domain pinning effects. This work provides comprehensive insights into the interplay between structural modifications and the resulting electrical and magnetic properties of BNdT-FCx ceramics, highlighting their potential for advanced multifunctional material applications.