Large dendritic oxide (hematite) was prepared by firing the mixture of a-Fe₂O₃ and Sb₂O₃ in the reducing atmosphere with the use of rice-chaff. The mechanism of the dendrite formation was interpreted as follows:
The early stage dissolution of a-Fe₂O₃ into Sb2O3 melt is followed by the evaporation of Sb₂O₃ with the increase of temperature, which consequently leads to the precipitation of dendritic nuclei of magnetite (Fe₂O₄) on the melt surface, because of strongly reducing atmosphere. The mixed melt climbs through the dendrite nuclei by the capillary action, and the successive evaporation of the solvent (Sb₂O₃) results in the rapid growth of Fe₂O₄ dendrite. Since the dendrites have large surface area, they are readily reoxidized to ferric oxide (a-Fe₂O₃) during cooling stage, retaining the skelton structure of the magnetite dendrite.