Effect of A site and B site doping on structural, thermal, and dielectric properties of BiFeO_3 ceramics

摘要

Polycrystalline Bi_(1-x)Ba_xFe_(1-y)M_yO_3 (M = Co and Mn; x = 0.1, y = 0.1) were synthesized by solid-state route method to study the compositional driven structural transformations in multiferroics. Room temperature X-ray diffraction patterns confirmed the formation of perovskite structure. Rietveld-refined crystal structure parameters revealed the existence of rhombohedral R3c symmetry for both the samples. The samples were found to be nearly free from any other secondary phases. Raman analysis reveals that Ba atom substitutes Bi site and Mn and Co atom substitutes Fe site into the BiFeO_3 with the shifting of phonon modes. The red shift is attributed to Co or Mn doping where as blue shift occurs from Ba doping. The differential scanning calorimetry reveals the corresponding Neel temperature 370 °C and 326 °C for Co and Mn doped samples. Ba and Co substitution with x=0.1 and y=0.1 has not affected the Neel temperature of the parent BiFeO_3 as well of Ba and Mn substitution. The variation of frequency dispersion in permittivity and loss pattern due to A-site and B-site substitution in BiFeO_3 was observed in the dielectric response curve.