In-situ XRD study of the crystal size transition of hydroxyapatite from swine bone

Abstract Hydroxyapatite was obtained from swine bones (P-HAp) and then, in situ, analyzed using differential scanning calorimetry (DSC) and high-temperature X-ray diffraction (HT-XRD). In situ X-ray patterns were obtained every 20 °C from 400 to 900 °C, with heating rates: 3, 6, and 9 °C/min. P-HAp was also calcined into a furnace to correlate the morphological properties with in situ measures. P-HAp is composed of nanometric like-plates crystals that exhibit high atomic crystalline order that become micrometric after a transition around 720 °C, according to XRD patterns, the DSC thermogram, and electron microscopy images ex situ recorded. After that transition, the full width at the half maximum of in situ XRD patterns sharply comes down because the inelastic scattering contribution decreases. In the case of nanocrystals, the pore size and surface area are governed by the intra-crystal spacing, while for microcrystals, they are governed by the inter-crystal spacing.