Sol-gel preparation of alumina gels forming alpha-alumina around 500 degrees C

The alumina gels which form alpha-Al2O3 at heat treatment temperature as low as similar to 500 degrees C were prepared from aluminum-sec-butoxide by the sol-gel method under the ambient condition. Preparation of transparent alumina sol by hydrolysis of the alkoxide at a low temperature such as 0 degrees C and aging the sol at a moderately low temperature, typically 8 degrees C for a relatively long time up to 30 days were found to be important for obtaining such alumina gels.