Microwave rapid conversion of sol–gel-derived hydroxyapatite into β-tricalcium phosphate

Calcium phosphate-based biomaterials are of great interest due to their use in various biomedical applications. Current preparation methods of β-tricalcium phosphate (β-TCP) require the processing of calcium phosphate precursors at high temperatures for long periods. Sol–gel-derived calcium-deficient carbonated hydroxyapatite (CHA) samples were synthesized and then aged at different times (24 and 90 h), while other freshly prepared samples were subjected to microwave (MW) radiation for 10 min in order to prepare β-TCP. All samples were calcined (at 750 °C) and then were characterized using scanning electron microscopy, Fourier transform infrared spectroscopy and X-ray diffraction. The 24-h-aged samples showed complete degradation into β-TCP and calcium pyrophosphate (CPP) phases. However, only β-TCP phase was detected in the 90-h-aged samples. Furthermore, β-TCP as the major phase was also obtained in the 10-min MW-treated unaged samples. The aging of sol–gel-derived CHA samples for 90 h had a positive effect on the conversion of CHA into β-TCP phase. Furthermore, the MW treatment of the unaged CHA samples enhanced its total conversion into β-TCP in shorter time which could be attributed to the MW irradiation-induced effect on the CHA structure.