Hydroxyapatite powders and thin films prepared by a sol-gel technique

The formation of hydroxyapatite (HA) from a sol-gel precursor was studied using X-ray diffraction (XRD). The sol-gel was processed into both powders and thin films. The effect of drying and firing temperatures on the HA phase formation was studied. Thin HA films up to 1 μm thick were deposited on silicon wafers coated either with borophosphate silicate glass (BPSG) or titanium films, dried and then fired. Increasing the drying temperature raised the firing temperature for initial formation of crystalline HA. It was found that at firing temperatures ranging from 300 to 1000°C, the dominant phase in the powders was HA with small amounts of calcium oxide and β-tricalcium phosphate (β-TCP). As the firing temperature increased the amount of CaO and (β-TCP increased. At firing temperatures ranging from 300 to 500°C the only observable crystalline phase in the films was HA.