COMPARATIVE-STUDY OF THE EFFECTS OF RARE-EARTH IONS IN A HIGH-FREQUENCY NI-ZN FERRITE

Some effects of the rare-earth ions on the properties of the polycryst alline stoichiometric ferrite with formula Ni-0 7Zn0.3Fe1.98R0.02O4(R= Yb, Er, Dy, Tb, Gd, Sm and Cc) are described. The results obtained rev eal that by introducing a relatively small amount of R2O3 instead of F e2O3, an important modification of both structure and properties can b e obtained. R2O3 facilitates the formation of the crystalline secondar y phases (orthoferrite, garnet) on the grain boundary which inhibit th e ferrite grain growth. The R ions tend to flatten the mu(i)-T curve, shift the Curie point to lower temperature and increase the electrical resistivity. The variation of these properties with the R species has been explained as an effect of the ionic radius size which varies fro m 0.86 for Yb to 1.07 for Ce.