Posner’s cluster

Reactions (1) and (2) have been postulated by Kokubo (1997) and subsequently electrochemically confirmed. The conversion of amorphous calcium titanate to calcium phosphate (Figure 5.2d,e) may be initiated by the formation of a thin layer of calcium phosphate with the configuration of the Posner s cluster, Ca3(P04)2 3 (reaction (5)) that has been shown to have the energetically most stable configuration (Onuma et al., 2000). This amorphous layer takes up more calcium and phosphate ions from the SBF to form OCP (reaction (6)) with Ca/P = 1.33 and finally stoichiometric hydroxyapatite (reaction (7)) with... 

---