Structure, magnetic and electrical properties of Ba-modified Bi₂Fe₄O₉

Bi_2−xBa_xFe₄O₉ material (0 ≤ x ≤ 0.125) has been synthesized by sol–gel method. Structural characterization shows the single phase of orthorhombic Bi₂Fe₄O₉. Moreover, the structure of Bi_2−xBa_xFe₄O₉ gradually presents a regular variation with increasing Ba content. Surface morphology of the samples is examined showing homogeneous grain distribution accompanied by the decreasing grain size with increase of Ba. Due to doping Ba, magnetic properties are significantly enhanced shown as the increasing remnant magnetization and saturation magnetization. Dielectric constant shows the increasing tendency with colossal values especially at high temperature range. In addition, the real part of ac conductivity exhibits the increasing trend with increasing frequency and the content of Ba. The analysis of impedance spectrum also suggests the increasing conductivity. The improvement in magnetic and electrical properties of Bi₂Fe₄O₉ by substitution of Ba can be attributed to the different ionic radius of Ba²⁺ from Bi³⁺ to Fe³⁺ which results in the change of magnetic structure and morphology.