Hydroxyapatite (HAp) derived from the scallop shell was successfully prepared using a precipitation method and varying the Ca/P concentration. Scallop shells were calcined at 1000°C to produce CaO. The precursors were a Ca(OH)₂ suspension and an H₃PO₄ solution, and the HAp was synthesized by mixing the two precursors and calcining at 1050°C. The aim of this study was to investigate the effect of Ca/P concentration. Samples were characterized by XRD, SEM-EDX, and FTIR. The XRD patterns indicated an increase in crystallinity with increasing Ca/P concentration ratio. The lattice parameter and the density values of the 0.5/0.3 sample approached the theoretical value. The crystallite sizes of HAp powders ranged from 79.750 ± 0.066 to 90.932 ± 0.071 nm. The Ca/P ratios of 0.5/0.3 and 1/0.6 were 1.68 and 1.67. The FTIR spectra confirmed the presence of functional groups of PO43- and OH-.
