The effect of TiO₂ on the magnetic power losses and electrical resistivity of polycrystalline MnZn-ferrites

In this paper the mechanism through which TiO2 affects the magnetic power losses of iron excess polycrystalline MnZn-ferrites is investigated. It has been found that TiO2, on being diluted in the bulk of the grains, promotes the homogeneous accumulation of calcium and silicon along the grain boundaries, by providing high specific resistivity properties to the resulting microstructure. This calcium and silicon segregation enhancement is attributed to the increased cation vacancy concentrations associated with the incorporation of tetravalent Ti in the spinel lattice. The creation of cation vacancies through a dopant such as Ti does not have the same effect as the creation of cation vacancies through control of the partial pressure of oxygen during firing. The latter is believed to promote calcium and silicon accumulation at the pores and the triple points rather than along the grain boundaries, resulting thus in microstructures with reduced specific resistivity.