INFLUENCE OF THE ADDITION OF BI2O3 ON THE GRAIN-GROWTH AND MAGNETIC-PERMEABILITY OF MNZN FERRITES

Additions of Bi2O3 were used to promote grain growth and to increase m agnetic permeability during sintering of MnZn ferrites, The results sh owed that small additions of Bi2O3 of <0.05 wt% remarkably increase th e permeability of MnZn ferrites, On the other hand, addition of 0.05 w t% Bi2O3 induced the formation of a microstructure composed of giant g rains with trapped pores embedded in a normal microstructure. The perm eability of these samples showed a pronounced secondary maximum in per meability, At still higher Bi2O3 concentrations, above 0.2 wt%, the gr ain growth was retarded and a normal microstructure appeared; however, the magnetic permeability was strongly reduced.