Preparation of Strontium-Barium Hydroxyapatite by Coprecipitation

This paper reports a novel coprecipitation process for the preparation of strontium-barium hydroxyapatite [Sr5-xBax(PO4)(3)OH]. Strontium nitrate, barium nitrate and phosphoric acid were dissolved in water to form a homogeneous Sr-Ba-P aqueous solution. The samples were characterized by powder X ray diffraction, Fourier transformed infrared spectroscopy and scanning electron microscopy. The results showed that the barium phosphate [Ba-3(PO4)(2)] phase appeared at the samples prepared at the pH value lower than 12. A series of Sr5-xBax(PO4)(3)OH samples had beenobtained by adding sodium hydroxide aqueous solution into the Sr-Ba-P solution to pH12.5 and following aging at 60 degrees C for 24h. The so-prepared samples are metallic cation-deficient hydroxyapatite solid solutions. The samples present low degree of crystallinity, irregular short rod-like morphology and nanometer size. The crystal cell parameters of Ca5-xSrx(PO4)(3)OH samples are nearly linear to their barium content, and their infrared absorption bands of PO43- groups shift to lower wave numbers with the increase of the barium content.