Grain boundary impedance of doped Mn-Zn ferrites

The electrical properties of Mn-Zn ferrites undoped and doped with Nb2O5 an d V2O5 were investigated by impedance spectroscopy. The observed impedance response corresponded to that of a highly resistive grain boundary componen t 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 bet ween bulk and grain boundary components. The different dopant performance o f these two components is discussed on the basis of grain boundary structur e and chemical data, electrical conductivity, and dielectric dispersion.