THE EFFECT OF BINDER ADDITIONS ON THE GREEN AND SINTERED PROPERTIES OF MN-ZN FERRITE CERAMICS

The suitability of three candidate binders for use in the production o f Mn-Zn ferrite has been investigated. A Lab-top spray dryer was used to coat mixed oxide-prepared ferrite powder with binder. The powder ob tained from the Lab-top spray dryer was an order of magnitude smaller than commercially prepared powder. Pressed powder compacts prepared fr om the two types of powder exhibit similar green strengths, and the si ntered products exhibit similar magnetic properties and microstructure s. The use of poly(vinyl alcohol), poly(ethylene glycol) or poly(acryl amide) as a binder for Mn-Zn ferrite yielded specimens with measurabl e flexural green strengths, typically 0.2 MPa for PVA and PAM and 0.15 MPa for PEG (at similar to 1 wt% binder level). After sintering, such specimens exhibited good magnetic properties (initial permeabilities similar to 2500) end the fired densities were at least 90% theoretical . Specimens prepared with higher binder contents had marginally lower densities and lower initial permeabilities. The solid hydrocarbon resi due left after the low temperature burnout of PVA and PAM binder does not cause a measurable degradation of the magnetic properties or affec t the microstructures of sintered products.