Chemical and structural changes of hydroxyapatite films by using a sol-gel method

Hydroxyapatite coatings were prepared onto Si(100) substrates by using a sol-gel method with calcium nitrate and phosphoric acid as starting materials. Precursor sols were spin-coated onto the substrates and prefind at 300 degrees C for 60 s in air. Formation of the hydroxyapatite structure was observed at 500 degrees C by X-ray diffraction and a beta-tricalcium phosphate phase was formed at 700 degrees C. According to the results of Fourier transform infrared spectroscopy, the formation of a beta-tricalcium phosphate is discussed on the basis of the decomposition of carbonated hydroxyapatite. (C) 1999 Elsevier Science S.A. Ail rights reserved.