Synthesis and Sintering of Calcium Hydroxyapatite for Biomedical Applications

Hydroxyapatite (HAp) owns various properties, which are required for bone tissue engineering applications. These properties include bioactivity, biocompatibility, osteoconductivity, and osseointegration. Based on these properties, HAp has been utilized as one of the most studied materials for various load-bearing biomedical applications. However, obtaining a pure HAp phase remains a challenge for biomaterial researchers. In order to understand the phase generation, it is essential to scrutinize the synthesis procedures along with the sintering of the HAp for biomedical applications. In this regard, we explained the crystal structure and the bond energy of the HAp lattice, which govern the degradation of the HAp, suitable for various biomedical applications. This discussion is followed by the practical synthesis procedures for obtaining controlled size and morphology of the HAp, which remain another key factor for the biological responses of the HAp based scaffolds and implants for bone tissue engineering. Further, we scrutinized the effect of sintering temperature and its role in phase generation. We summarized the crystal structure, synthesis processes, and effect of calcination, and sintering over the phase generation of the calcium phosphate biomaterials. It was observed that the optimum temperature, pH, and sintering temperature together remain the deciding factor for the phase generation.