Perfect single-crystal alumina microspheres

We report the synthesis of perfect single-crystal Al₂O ₃ microspheres via direct thermal decomposition of aluminum isopropoxide in air without any template or catalyst. The obtained microspheres were characterized using scanning electron microscopy, X-ray diffraction, transmission electron microscopy, and selective area electron diffraction. The results suggested that the formation of the spheres can be attributed to a transition from polycrystalline to single-crystalline symmetry during high-temperature annealing. The obtained microspheres could be useful for many applications such as lubricants and polishing mediums.