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Tailoring structural, electrical, and magnetoelectric properties of BiFeO3 ceramics via low-level cobalt substitution

Year: 2026

Type: article

Abstract: This study presents a comprehensive investigation of the structural, microstructural, electrical, magnetic, and magnetoelectric properties of BiFeO3 ceramics doped with low concentrations of cobalt (1%, 1.5%, and 2% molar at the Fe site). X-ray diffraction combined with Rietveld refinement confirms the retention of the rhombohedral R3c structure across all compositions, with a systematic contraction of lattice parameters attributed to the smaller ionic radius of Co3+ compared to Fe3+. Microstructural analysis reveals a doping-induced evolution from heterogeneous grain growth and high microstrain at intermediate doping levels to a more refined and compact microstructure at 2% Co, suggesting the presence of stress relaxation mechanisms. Electrical measurements demonstrate that cobalt doping significantly modulates resistivity and temporal stability, with the 2% Co sample exhibiting enhanced stability and lower resistivity due to improved charge transport pathways. Dielectric analysis indicates a trade-off between permittivity and losses: while low doping favors dielectric stability with minimal conduction losses, higher cobalt content enhances permittivity at the expense of increased dielectric losses driven by defect-mediated hopping conduction. Magnetic characterization reveals a progressive collapse of the cycloidal spin structure, resulting in enhanced remanent magnetization, coercivity, Rayleigh nonlinearity, and magnetic energy dissipation. Magnetoelectric coupling exhibits a strong dependence on doping levels, with robust intrinsic coupling at 1% Co transitioning to defect-driven extrinsic behavior at higher concentrations. These findings establish cobalt substitution as an effective strategy for tailoring the multifunctional properties of BiFeO3, providing key insights into the interplay between structural distortions, defect chemistry, and functional performance in multiferroic perovskite systems.

Source: Journal of Alloys and Compounds

DOI: 10.1016/j.jallcom.2026.186070