Well-crystallized alpha-calcium sulfate hemihydrate (alpha-CSH) powders useful for bone defect filling were synthesized using a salt solution method and their morphologies were effectively modified by adjusting the pH of the reaction solutions or by adding succinic acid. The effect and its mechanism of the pH and the succinic acid on the phase composition and the morphology of the crystals were discussed in detail. (c) 2013 Elsevier B.V. All rights reserved.