HOMOGENEOUS GRA1N GROWTH AND FAST-FIRING OF CHEMICALLY MODIFIED NANOCRYSTALLINE MnZn FERRITES

摘要

A chemical method utilizing sol-gel reactions was investigated to uniformly incorporate small amounts of additives of Si and Ca into nanocrystalline Mno.6Zn0.4Fe_2O_4 powders (≈ l4 nm particle size). Sintering behavior of the chemically modified nanocrystalline MnZn ferrites was studied with regard to the effects of the chemical additives and sintering conditions on densification and grain growth. The nanopowder samples without the additives exhibited abnormal grain growth regardless of heating rate after pressing at a relatively low pressure and sintering at l200 C, while the chemical addition of 2 wt/100 SiO_2 and 0.5 wt/100 CaO was found to improve microstructural characteristics, i.e., homogeneous grain growth and less porosity. Fast-firing did not seem to favorably affect densification of the chemically modified MnZn ferrite nan- opowder, but was found to contribute to the suppression of grain growth in the nanocrystalline ferrite compacts.