Effect of Processing Parameters on Microstructure Development and Magnetic Spectrum of Ni0.3Zn0.7Fe2O4 Ferrite: I—Ferritisation and Microstructure Development

Nickel-Zinc ferrites of nominal composition Ni0.3Zn0.7Fe2O4 were prepared with small deviations from stoichiometry by standard ceramic powder processing. Ferritisation was carried out in the range 800–1100°C and the progress was studied by X-ray diffractograms. For the final selected material ferritisation was done at 850°C. The ground ferritised material with a particle size of about 0.1 micron was compacted into pellets for densification and microstructure studies, and toroids for magnetic studies under identical compaction pressures. Pellets and toroids were packed in fireclay saggars with Ni-Zn ferrite powder of similar composition to avoid loss of Zn at sintering temperatures. Firing was done in silicon carbide tube furnace at 1150, 1170, 1200, 1250 and 1300°C for 5, 20 and 100 hrs. Bulk density and porosity were determined and microstructure analysis was made on polished and etched specimens of fired pellets. Grain size and pore size distributions were determined from optical micrographs. Maximum fi...