A new solid precursor, hydrous aluminum oxide, for alpha-alumina nanoparticles was prepared by thermal decomposition of aluminum triisopropoxide (ATI) vapor in a 500 mL batch reactor at 170-250 degrees C with HCl as catalyst. The conversion of ATI increased with increasing temperature and catalyst content; it was nearly complete at 250 degrees C with the catalyst at 10 mol% of the ATI. The obtained precursor particles were amorphous, spherical and loosely agglomerated. The primary particle size is in the range 50-150 nm. The ignition loss of the precursor was 24%, considerably lower than 35% of Al(OH)(3), the popular precursor for alumina particles. Upon calcination of the precursor at 1200 degrees C in the air with a heating rate of 10 degrees C/min and a holding time of 2 h, the phase was completely transformed into alpha. The spherical particles composing the precursor turned worm-like by the calcination probably due to sintering between neighboring particles. The surface area equivalent diameter of the resulting alpha-alumina was 75 nm. (C) 2011 Elsevier Ltd. All rights reserved.