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) via controlled sintering temperature (650–1050 °C) and dwell time (3–9 h). The effects of these parameters on the HA's structure and composition were systematically investigated. X-ray diffraction analysis revealed a direct correlation between sintering conditions and crystallite size, which increased from 32 nm to 85 nm with rising temperature and time. Energy-dispersive X-ray spectroscopy 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-hour dwell time. Fourier-transform infrared spectroscopy confirmed the presence of characteristic HA functional groups, while scanning electron microscopy indicated improved particle interconnection and reduced agglomeration at higher sintering temperatures. The findings establish controlled sintering as a critical and effective strategy for customizing the properties of bio-waste-derived HA, enhancing its potential for targeted biomedical applications by achieving bone-like stoichiometry and desirable microstructure.