Corundum (alpha-Al2O3) is the only stable oxide in the aluminium-oxygen system and is characterized by its high mechanical and chemical stability. But there are some problems in producing very fine corundum powders. Usually alpha-Al2O3 is obtained from transition aluminas at temperatures in the range of 1100-1200 degrees C. At this temperatures the dispersity of the corundum formed is reduced due to the start of grain growth processes. That is the reason for our investigations in preparing alpha-Al2O3 at lower temperatures. Therefore aluminium-secondary-butoxide was hydrolysed in water and seeded with different amounts of hematite. The dried powders were investigated for instance by using differential thermal analysis. A nearly linear relation between seeding amount and transformation temperature was found. The formation temperature of corundum was decreased by seeding with 10 wt% hematite from about 1100 to 970 degrees C.