Effect of Tb-Mn substitution on the magnetic and electrical properties of BiFeO3 ceramics

Tb-Mn co-substituted BiFeO3 of stoichiometry Bi1−xTbxFe1−xMnxO3 (x=0, 0.10, 0.15, 0.20) has been synthesized by a solid-state reaction method. Inferences from X-ray photoelectron spectroscopy indicate the presence of Fe in mixed oxidation states i.e., Fe3+ and Fe2+. But in the Tb-Mn substituted samples, Fe is predominantly in +3 oxidation state and Mn is found to be in +3 state. There is a decrease in cell volume due to Tb3+ substitution as Mn3+ ions have similar ionic radii as that of Fe3+. The grains of substituted samples have regular dimensions with agglomeration when compared to irregular shaped grains of BiFeO3. No major characteristic transitions are found in substituted samples as observed from the thermal measurements, but BiFeO3 shows a ferroelectric−paraelectric transition at ~820 °C. A weak magnetic ordering is observed from the magnetization measurements at room temperature with the increase in substitution percentage. Impedance spectroscopy studies show the impact of Tb-Mn substitution on the conductivity of BiFeO3. The ferroelectric loop and leakage current studies with an applied electric field on samples also supplement the results obtained from impedance measurements.