Spherical tricalcium phosphate (TCP) micro-granules were prepared using a jet wheel impact atomization and calcination process. Spherical TCP granules were obtained which can exhibit phase transformation between the alpha and beta polymorphs as a function of the heating temperature. The progressive changes in the phosphate group of TCP granules were attributed to the phase transformation. Consequently, such structural changes in the TCP micro-granules can be used to control the dissolution and degradation of TCP through the controlled density and microporosity of the micro-granules. (C) 2014 Elsevier B.V. All rights reserved.