Synthesis and microstructural characterization of nano-size calcium phosphates with different stoichiometry

• Published in: Ceramics international 2011-04, Vol.37 (3), p.971-977
• Main Authors: Ergun, Celaletdin, Evis, Zafer, Webster, Thomas J., Sahin, Filiz Cinar
• Format: Article
• Language: English
• Subjects: Bioceramics; Calcium phosphate; Calcium phosphates; Characterization; Diffraction; Hydroxyapatite; Microstructure; Nanomaterials; Nanostructure; Orthopedic implants; Phases; Porosity
• ISSN: 0272-8842; 1873-3956
• DOI: 10.1016/j.ceramint.2010.11.004

Calcium phosphates with Ca/P molar ratios of 0.5, 0.75, 1.33, 1.5, 1.55, 1.67, 2.0, and 2.5 were synthesized by a wet chemistry precipitation method and sintered at 500°C, 700°C, 900°C, 1100°C and 1300°C for 2h. Presence of phases and microstructures of calcium phosphates were determined by X-ray diffraction and scanning electron microscopy. In all different Ca/P ratios, the precipitated phase was always hydroxyapatite with very small size and/or partial disorderness regardless of the Ca/P ratios in the starting precipitating medium. For samples with 0.5 and 0.75 Ca/P ratios in starting solution, tricalcium phosphate and calcium pyrophosphate phases were observed. In contrast, for samples with 1.0 and 1.33 Ca/P ratios, the only stable phase was tricalcium phosphate. For the samples with Ca/P ratio of 1.5, the tricalcium phosphate phase was dominant. However, small amounts of hydroxyapatite started to appear. For samples with Ca/P ratio of 1.67, the hydroxyapatite phase was dominant. Lastly, for samples with the Ca/P ratios of 2.0 and 2.5, the CaO phase started to appear in addition to the hydroxyapatite phase which was the dominant phase. Moreover, the average grain size, porosity (%) and the average pore size decreased with increasing the Ca/P ratios.