Characterization of silicon-substituted hydroxyapatite powders synthesized by a wet precipitation method

Abstract

The preparation of nano sized silicated hydroxyapatite Ca 10 (PO 4) 6-x (SiO 4) x (OH) 2-x (Si-HA) with three different silicon concentrations were investigated using a wet precipitation method. The effects of the Si substitution on crystallite size, lattice parameters and fraction of crystalline phase of the powders were discussed. The crystalline phase, chemical composition,and crystallite size of hydroxyapatite and silicon substituted hydroxyapatites were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), inductively coupled plasma and transmission electron microscopy. The crystallite size and fraction of crystalline phase decreases with increase in silicon content and particle morphology spheroidal for pure hydroxyapatite changes to elongated ellipsoidalcrystals while silicon substitution increases. FTIR analysis reveals, the silicon incorporation to hydroxyapatite lattice occurs via substitution of silicate groups for phosphate groups. Substitution of phosphate group by silicate in the Si-HA structure results an increase in the lattice parameters in both a-axis and c-axis of the unit cell.