Hydroxyapatite, tricalcium phosphate and biphasic materials prepared by a liquid mix technique

The Pechini based liquid-mix technique has been applied to prepare either single phases of hydroxyapatite –Ca10(PO4)6OH2– (OHAp), α and β-tricalcium phosphate –Ca3(PO4)2–, (α-TCP, β-TCP) or biphasic calcium phosphates (BCP). Compositions with a Ca/P molar ratio between 1.5 and 1.667 were synthesized and subjected to a thermal treatment up to 1400 °C. α and β-TCP were both prepared from a Ca/P ratio of 1.5, but while β-TCP is isolated at 900 °C and remains stable up to 1100 °C, it is necessary to anneal at 1400 °C for 72 h to obtain pure α-TCP. OHAp is obtained as a single phase from a 1.667 Ca/P ratio after annealing at 1000 °C for 24 h and starts to decompose at 1400 °C. Between these two extremes a whole range of biphasic calcium phosphates can be prepared by using this technique with an accurate control of the starting reactants. These materials have been characterized by FTIR, XRF, BET, XRD and, based on this technique, a phase quantification determination (QXRD). The solubility of these products was tested in a buffered solution at 37 °C and pH=7.4.