Controlled Synthesis Of Hexagonal Alpha-Fe2o3 Crystals For Ceramic Colors By Hydrothermal Reaction Of Fecl3 And Naoh Solutions

The effect of mixing process of FeCl3 and NaOH solution on the formation of platy (hexagonal) alpha-Fe2O3 was investigated at 160 and 180 degrees C by the hydrothermal process. The crystal growth of platy alpha-Fe2O3 was promoted at higher hydrothermal temperature, higher concentration of NaOH solution and by the addition of FeCl3 solution to NaOH solution instead of the reverse addition. Platy crystals of alpha-Fe2O3 showed dark red wine color while nanophase equiaxed crystals showed yellowish red color. The platy crystals of 3-6 mu m in average diameter kept their platy structure after heating at 900 and 1100 degrees C in air due to their higher thermal stability towards sintering.