Calcium phosphate powders were synthesized with Ca/P molar ratios of initial reagents ranging from 1.660 to 1.667 using wet precipitation method. This work deals with allocating a specific temperature level to each H3PO4 solution and Ca(OH)(2) suspension prior to the mixing process, and studying their influences on powder composition. A high pH value of the synthesis medium and the incorporation of numerous carbonate ions into the structure were attained by dropping the temperature of the Ca(OH)(2) suspension down to 5 degrees C. X-ray diffractometry and FTIR spectroscopy showed that heating samples that had a medium temperature exceeding 25 degrees C resulted in the dominant HAp phase, regardless of the initial acid solution temperature. By maintaining the medium temperature at 5 degrees C, a sudden formation of the beta-TcP phase occurred after thermal treatment at 1300 degrees C, and this trend continued with the concurrent decrease in the temperature of the initial acid solution. An interpretation of the formation mechanism under these low-temperature conditions is proposed in terms of the temperature and pH value of the medium and the state of the phosphate and carbonate ions. (C) 2011 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.