Tailoring the crystallite size and stoichiometry of hydroxyapatite from buffalo bone waste via controlled sintering temperature and time

This study demonstrates the precise tailoring of the crystallite size and stoichiometry of hydroxyapatite (HA) derived from buffalo bone waste ( Bubalus bubalis ) by controlling sintering temperature (650–1050 °C) and dwell time (3–9 h). The effects of these parameters on the structure and composition of HA were systematically investigated. X-ray diffraction analysis revealed a direct correlation between the sintering conditions and crystallite size, which increased from 32 to 85 nm with increasing temperature and time. Energy-dispersive X-ray spectroscopy analysis showed that the Ca/P ratio could be modulated within a range of 1.31 to 1.71, with the ideal stoichiometric ratio of 1.67 achieved specifically at 850 °C with a 7 h dwell time. Fourier-transform infrared spectroscopy confirmed the presence of the characteristic HA functional groups, whereas scanning electron microscopy analysis indicated improved particle interconnections and reduced agglomeration at higher sintering temperatures. These findings establish controlled sintering as a critical and effective strategy for customizing the properties of biowaste-derived HA and enhancing its potential for targeted biomedical applications by achieving bone-like stoichiometry and desirable microstructures.