Mixtures of aluminum isopropoxide and tetraethoxysilane in 1,4-butanediol were autoclaved at 300 degrees C for 2 h. The products were then calcined in air to yield silica-modified aluminas. These silica-modified aluminas had high alpha-alumina-transformation temperatures and maintained significantly large surface areas at elevated temperatures (1000-1300 degrees C). For example, the. product prepared from a mixture of Al/Si ratio 8 transformed into alpha-alumina at around 1500 degrees C, and it possessed a surface area of 55 m(2)/g, even after calcination at 1300 degrees C for 30 min.