Synergetic enhancement of dielectric performance and charge transport mechanisms in La3+/Ni2⁺ co-doped rhombohedral BiFeO3 ceramic

This investigation is focused on lanthanum and nickel co-doped BiFeO 3 compound prepared using sol–gel auto combustion technique. The rhombohedral distorted structure of the space group ( R-3 m ) was confirmed through X-ray diffraction (XRD) analysis with secondary phase Bi 12.5 Fe 0.5 O 19.5 . The crystallite size was calculated to be 71.38 nm. The FE-SEM study revealed a compact polycrystalline microstructure containing closely packed well-defined grains. The Nyquist plots and impedance study indicate that both grain and grain-boundary thermally activated charge transport occur at higher temperatures. The activation energy needed to conduct electricity was determined to be 0.82 eV for both the grain and the grain boundaries, while the modulus showed the non-Debye type relaxation process happening between localised charge carriers associated with an activation energy of 0.29 eV. AC conductivity studies revealed thermally activated transport processes, indicating strong electron–phonon interaction and short-range hopping of charge carriers. The ceramic exhibited a remarkable dielectric constant ~ 3ⅹ10 3 at room temperature and 1 kHz frequency. The low dielectric loss (~ 0.63) indicated limited energy dissipation and improved dielectric efficiency of the material. The P-E hysteresis loop showed remanent polarization of 0.0414 μC/cm 2 and coercive field of 0.07 kV/cm at room temperature. These findings provide insight into the interplay between defect structure, interfacial polarization, and charge-transport mechanisms in La/Ni-modified BiFeO₃ ceramic.