Homogeneous grain growth and fast-firing of chemically modified nanocrystalline MnZn ferrites

A chemical method utilizing sol-gel reactions was investigated to uniformly incorporate small amounts of additives of Si and Ca into nanocrystalline Mn_0.6Zn_0.4Fe₂O₄ powders (≈ 14 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 1200°C, while the chemical addition of 2 wt% SiO₂ and 0.5 wt% 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 nanopowder, but was found to contribute to the suppression of grain growth in the nanocrystalline ferrite compacts.