EFFECT OF HEAT-TREATMENT ON PULSED-LASER DEPOSITED AMORPHOUS CALCIUM-PHOSPHATE COATINGS

Amorphous calcium phosphate coatings were produced by pulsed laser dep osition from targets of nonstoichiometric hydroxyapatite (Ca/P = 1.70) at a low substrate temperature of 300 degrees C, They were heated in air at different temperatures: 300, 450, 525 and 650 degrees C, Chemic al and structural analyses of these coatings were performed using X-ra y diffraction (XRD), FTIR, and SEM, XRD analysis of the as-deposited a nd heated coatings revealed that their crystallinity improved as heat treatment temperature increased, The main phase was apatitic, with som e beta-tricalcium phosphate in the coatings heated at 525 and 600 degr ees C. In the apatitic phase there was some carbonate substitution for phosphate and hydroxyl ions at 450 degrees C and almost solely for ph osphate at 525 and 600 degrees C as identified by FTIR, This was accom panied by a higher hydroxyl content at 525 and 600 degrees C. At 450 d egrees C a texture on the coating surface was observable by SEM that w as attributable to a calcium hydroxide and calcite formation by XRD, T hese phases almost disappeared at 600 degrees C, probably due to a tra nsformation into calcium oxide. (C) 1998 John Wiley & Sons, Inc.