The great capability of high-energy ball milled basic polyaluminium chloride gel (PACI) which consisted of the monomeric Al3+ ions and polymerized Al3+ species such as [Al13O4(OH)(24)(H2O)(12)](7+) with a Keggin like structure to enhance the phase transformation into alpha-Al2O3 nanocrystals at low temperature was verified. PACl gel 10 min milled and annealed at 400 degrees C, partially transformed to nanocrystalline alpha-Al2O3 with the mean XRD crystallite size in the range of 15-17 um, embedded in an amorphous or transition alumina matrix. Further crystal growth up to similar to 50 um and phase pure alpha-Al2O3 powder was obtained when heat-treated at 1000 degrees C. In contrast to this, the non-milled PACI gel transforms to the transition theta-Al2O3 phase at 1000 degrees C. The evolution of alpha-Al2O3 nanocrystals was studied by XRD, TEM, selected area electron diffraction (SAED) and high-resolution transmission electron microscopy (HRTEM) methods. (C) 2011 Elsevier Ltd. All rights reserved.