This study focus on the synthesis of Ca-deficient apatites (CDA) by using the wet chemical precipitation method in demineralised water solutions at pH=7 and synthesis temperature of 90 °C. Upon calcination at 1000°C, the resulting HAP powders decomposed leading to the formation of small amounts of β-TCP. Surprisingly, under some conditions, minor amounts of α- TCP were also formed at 1000°C together with β-TCP. The appearance of α-TCP is favoured by the absence of mineral ions in the precipitation medium, which in turn depends on the purity of the water used. Factors affecting the formation of both β-TCP and α-TCP are discussed.