Grain boundary impedance of doped Mn–Zn ferrites

The electrical properties of Mn–Zn ferrites undoped and doped with Nb₂O₅ and V₂O₅ were investigated by impedance spectroscopy. The observed impedance response corresponded to that of a highly resistive grain boundary component in series with a less resistive bulk component. The presence of Nb⁵⁺ and V⁵⁺ led to an enhancement in the electrical resistance, especially in grain boundaries, as well as a greater difference in the electrical behavior between bulk and grain boundary components. The different dopant performance of these two components is discussed on the basis of grain boundary structure and chemical data, electrical conductivity, and dielectric dispersion.