Evaluation of phase transformation behavior in biphasic calcium phosphate with controlled spherical micro-granule architecture

Spherical biphasic calcium phosphate (BCP) micro-granules consisting of hydroxyapatite (HAp) and tricalcium phosphate (TCP) were prepared using a rotary spray drying and sintering process. A significant phase transformation of TCP in BCP granules occurred according to the relative content of HAp and TCP in the BCP granules depending on the sintering temperature. The crystal growth of HAp in BCP was suppressed by a phase transformation of TCP with a change in the electron density distribution in a crystal unit cell. In addition, these progressive changes in the hydroxyl and phosphate group of BCP granules might be due to the phase transformation of TCP. Consequently, such structural changes in the BCP granules led to an unexpected change in granule size and micro-cracks on their surface at high temperatures.