Effect of Ca and Mn Co-Doping on the Dielectric Properties of Nanocrystalline BiFeO 3

The influence of oxygen vacancies on dielectric properties of Ca and Mn co-doped bismuth ferrite, Bi 1−x Ca x Fe 1−x Mn x O 3 (BCFM) ceramics, synthesized by a modified sol-gel technique, has been investigated. X-ray diffraction reveals that the crystal structure transitions from R3c to the Pbnm space group with increasing co-doping concentration. The correlated barrier hopping conduction model applies up to a 10% co-doping concentration, while overlapping large polaron tunneling exists at concentrations above 20%. The dielectric study reveals strong frequency- and temperature-dependent dielectric parameters. The decrease in dielectric constant and loss with frequency is attributed to Maxwell-Wagner polarization, while the relaxation behavior follows a non-Debye mechanism; low dielectric loss at higher frequency indicates good dielectric stability and potential applications in electronic devices. The AC conductivity is lowest for the 5 mole % of Ca and Mn co-doped bismuth ferrite (BCFM-05) sample and exhibits an increasing trend with higher co-doping percentages. Also, the BCFM-05 sample exhibits the lowest dielectric loss. Thus, the optimized sample BCFM-05, with reduced AC conductivity and minimum dielectric loss, exhibits improved dielectric behavior in ceramics.