Monocalcium aluminate, CaAl2O4, is the main constituent of calcium alumina cements which have found wide applications in refractory industries. In the present work, CaAl2O4 nanoceramic compound was produced by high-energy ball milling of the oxide powders followed by annealing. The phase evolution and microstructural changes of the powders during the process were investigated by means of X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The results showed that no CaAl2O4 was formed during ball milling even after 100 h. By subsequent annealing, the nucleation and growth of CaAl2O4 took place at 1000 degrees C after 2 h. Depending on milling time, the amount of CaAl2O4 increased with increasing annealing temperature. The CaAl2O4 single phase was obtained by milling the sample for 100 h and subsequently annealing at 1200 degrees C for 2 h. The quantitative phase analysis was used to measure CaAl2O4 phases in these processes. The average particle diameter of the sample milled for 100 h and annealed at 1200 degrees C was found to be less than 100 nm as measured by transmission electron microscopy. (C) 2013 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.