Nanocrystalline calcium‐deficient hydroxyapatite prepared by a microwave‐assisted solvent‐free reaction

Abstract A microwave‐assisted solvent‐free synthesis of hydroxyapatite from calcium nitrate and sodium phosphate is reported. The product was characterized with respect to the presence of foreign ions and its thermal behavior. An apatite phase was formed in the mixture after irradiation with 2.45 GHz microwaves for 4 min at 350 or 700 W. Structurally, the product was a nanocrystalline calcium‐deficient hydroxyapatite (CDHA) with a Ca/P ratio around 1.5, containing some H 2 O, HPO 4 2– and CO 3 2– . After heating to 900°C for 1 h, β‐tricalcium phosphate (β‐TCP) was formed, demonstrating that this microwave‐assisted solvent‐free synthesis is well suited to prepare a precursor to bioceramics.