Structural Characterization of Microwave-Assisted Solution-Synthesized Strontium-Substituted Hydroxyapatite

Abstract

Hydroxyapatite and strontium-substituted hydroxyapatite nanoparticles (n-HA and Sr-HA) were prepared by microwave-assisted solution synthesis with aqueous solutions of various Sr/(Sr[Formula: see text]Ca) molar ratios ranging from 0% to 15%. The structural properties of the hydroxyapatite powders were investigated by X-ray powder diffraction, Fourier transform infrared spectroscopy and Raman spectra, field emission scanning electron microscopy coupled with energy dispersive X-ray spectrometry and transmission electron microscopy. The results confirmed that strontium ions had been incorporated into the hydroxyapatite lattice. The synthetic n-HA and Sr-HA nanocrystalline consisted of hydroxyapatite crystalline phase with hexagonal structure, and the particle size was 30–40 × 60–70[Formula: see text]nm and 40–50 × 70–80[Formula: see text]nm, respectively. The calcined HA particle size ranged from about 120[Formula: see text]nm to 150[Formula: see text]nm, the calcined Sr-HA products were composed of spherical aggregates with a size of about 70–100[Formula: see text]nm. The incorporation of Sr ions lead to the formation of vacancies in the crystal structure of the HA. The results indicated that the strontium substitution did not change the crystal structures. More Sr resulted in less calcined crystallites and formed agglomerates owing to the size effect.