A novel synthetic approach to low-crystallinity calcium deficient hydroxyapatite

Abstract Synthetic calcium deficient hydroxyapatite (CDHA, with the formula Ca9(HPO4)(PO4)5OH) is a promising material which could be potentially used in biomedicine. The aim of this study was to develop a simple and cost-effective synthesis route for the preparation of low crystalline CDHA granules. A method based on an incessant dissolution-precipitation reaction eventually resulting in a solid and shaped material consisting of the desired phase was utilized. The calcium sulphate hemihydrate was selected as the starting material. The synthesis products obtained were characterized by Fourier transformed infrared spectroscopy (FTIR), X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM). The monophasic calcium deficient hydroxyapatite granules of about 300–350 μm in diameter were synthesized by three slightly different preparative approaches at 70 °C temperature and compared. Independently of the composition of the raw granules synthesized ones were composed of low crystalline an apatitic phase. The granules were calcium deficient as contained HPO42− group in their structure. It was demonstrated that the addition of (NH4)H2PO4 or (NH4)2HPO4 into the raw granules could promote the growth of the CDHA crystallites. SEM revealed that the microstructure of synthesized materials was influenced by the chemical composition of the raw granules. Chemical composition and presence of no an X-ray amorphous phase in obtained samples was confirmed by reheating the obtained granules at 800 °C to get monophasic β-TCP. Our work provides a novel and simple approach to produce CDHA granules for various applications.