Structural and dielectric properties of sol–gel synthesized (Mn, Cu) co-doped BiFeO₃ ceramics

BiFeO₃-based multiferroic ceramics if prepared in phase pure form possess wide range of applications based on their charming and switchable polarization, piezoelectric, magnetoelectric and spintronic properties. In this regard, we investigate the influence of Mn substitution at Fe-site in BiFe_0.99Cu_0.01O₃ samples, synthesized by sol–gel-based self-assisted combustion technique. Crystal structure was determined using X-ray diffraction which revealed a rhombohedrally distorted cubic perovskite structure of all the samples. The lattice constant increased, while crystallite size decreased with increased concentration of Mn. A systematic analysis of frequency-dependent dielectric constant, loss factor, tangent loss and impedance has been presented using an impedance analyzer. It is observed that the trend of dielectric constant, loss factor, tangent loss and impedance is decreasing with increasing frequency. It was also observed that electrical properties were mainly influenced by dominance of grain boundaries effect in 20 Hz–20 MHz range. Effect of increased concentration of Mn on frequency-dependent dielectric properties has also been discussed, and it is found that dielectric properties decreased with increasing concentration of Mn mainly attributed to the suppression of oxygen vacancies.