We investigated the transition between the monoclinic (P21/b) and hexagonal (P63/m) phases of hydroxyapatite, Ca5(PO4)3OH, both by X-ray diffraction (XRD) and differential scanning calorimeter (DSC) techniques. Peak intensities of XRD of the low-temperature monoclinic phase were almost unchanged up to 473 K but dropped abruptly to zero above 483 K. Endo- and exothermic DSC peaks and a specific heat anomaly associated with the transition were observed. The transition enthalpy and entropy were estimated to be 630 ± 25 J/mol and 1.30 ± 0.05 J/mol·K, respectively.
|Number of pages||3|
|Journal||Journal of Physical Chemistry|
|Publication status||Published - 1995 Dec 1|
All Science Journal Classification (ASJC) codes
- Physical and Theoretical Chemistry