Correlating Phase Evolution and Morphology of Hydroxyapatite–Titanium Composites With Titanium Content and Thermal Processing

Abstract Hydroxyapatite (HA) is a bioactive ceramic widely applied in dental, bone replacement, and implant therapies because of its excellent biocompatibility and chemical similarity to natural bone. Despite these advantages, its poor strength, limited thermal stability, low crystallinity, and unfavorable surface morphology restrict its use in demanding, load-bearing implants. Improving these properties without compromising biocompatibility remains a key challenge in developing reliable biomedical materials. In this study, HA–titanium (Ti) composites were synthesized by the wet precipitation method and examined to understand how Ti content and processing temperature influence their structural and functional characteristics. Scanning electron microscopy (SEM) revealed distinct morphological changes: low Ti concentrations promoted finer, more uniform particles, whereas higher Ti content and elevated temperatures led to agglomeration, grain coarsening, and the appearance of rod-like TiO2 structures. X-ray diffraction (XRD) showed that crystalline HA was preserved at lower temperatures, with partial Ti addition into the HA lattice. At higher temperatures, reflections of rutile and anatase TiO2 phases emerged, indicating limited Ti solubility and the onset of phase segregation. Fourier-transform infrared (FTIR) spectroscopy confirmed these trends, with characteristic HA phosphate bands present across all samples, alongside band shifts, broadening, and diminished OH peaks that reflected lattice distortion. The growth of Ti– O bands at higher calcination temperatures further supported TiO2 formation. Collectively, these findings highlight that carefully controlled Ti incorporation enhances the crystallinity, thermal stability, and morphology of HA, while excessive Ti or high temperatures promote TiO2 segregation. Optimizing these parameters can pave the way for stronger, more reliable HA–Ti composites tailored for orthopedic, dental, and load-bearing implants that better serve patient needs.