Monodispersed barium titanate (BT) nanopowders with perovskite structure were successfully prepared by a solhydrothermal method. The results obtained from X-ray diffraction (XRD) revealed that BT particles with single cubic phase were favorably formed with low alkalinity, whereas tetragonal phase was observed with the enhancement of the alkalinity. Furthermore, electronic microcopy observations demonstrated that spherical aggregates of nanocrystals in final BT products transformed into mesocrystals with circular shape, and then into single crystals with rectangular shape as the alkalinity was elevated from 0.2 M to 1 M, concurrent with the decrease in average particle size. A mechanism involving the Ba/Ti ratio in the initial solution was proposed to illustrate the transformation of morphology and formation of crystals. (C) 2012 Elsevier B.V. All rights reserved.