Effect of rare earth radius and concentration on the structural and transport properties of doped Mn–Zn ferrite

Dielectric constant (ε′), AC conductivity (σ), and seebeck coefficient (S) have been measured for the ferrite samples of the general formula Mn0.5Zn0.5RyFe2O4; where R=Dy, Gd, Sm, Ce, and La prepared by standard ceramic technique and sintered at 1200 °C with a heating rate 4 °C/min. X-ray diffractograms show that all samples posses the spinel structure with the appearance of small peaks representing secondary phases. There is a lowering in the porosity starting after Sm-doped samples due to the presence of the secondary phases, which limits the grain growth. Due to seebeck measurements the manganese–zinc (Mn–Zn) ferrite doped with the rare earth has been classified as P-type semiconductors. It is possible to increase the electrical resistivity by using a small quantity of Dy3+ ions substitutions owing to the structural heterogeneity generated by the insulating intergranular layers. The isolation of the grains is the most promising approaches for further reduction in the eddy current losses at the operating frequencies.