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 of Mn-Zn ferrite has been investigated. A Lab-top spray dryer was used to coat mixed oxide-prepared ferrite powder with binder. The powder obtained from the Lab-top spray dryer was an order of magnitude smaller than commercially prepared powder. Pressed powder compacts prepared from the two types of powder exhibit similar green strengths, and the sintered products exhibit similar magnetic properties and microstructures. The use of poly(vinyl alcohol), poly(ethylene glycol) or poly(acryl amide) as a binder for Mn-Zn ferrite yielded specimens with measurable 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 residue left after the low temperature burnout of PVA and PAM binder does not cause a measurable degradation of the magnetic properties or affect the microstructures of sintered products.