Effect of heat treatment on pulsed laser deposited amorphous calcium phosphate coatings

García, F. and Arias, J.L. and Mayor, B. and Pou, J. and Rehman, I. and Knowles, J. and Best, S. and León, B. and Pérez-Amor, M. and Bonfield, W. (1998) Effect of heat treatment on pulsed laser deposited amorphous calcium phosphate coatings. Journal of Biomedical Materials Research Part A, 43 (1). pp. 69-76. ISSN 0021-9304

Abstract

Amorphous calcium phosphate coatings were produced by pulsed laser deposition from targets of nonstoichiometric hydroxyapatite (Ca/P = 1.70) at a low substrate temperature of 300 °C. They were heated in air at different temperatures: 300, 450, 525 and 650 °C. Chemical and structural analyses of these coatings were performed using X-ray diffraction (XRD), FTIR, and SEM. XRD analysis of the as-deposited and heated coatings revealed that their crystallinity improved as heat treatment temperature increased. The main phase was apatitic, with some β-tricalcium phosphate in the coatings heated at 525 and 600 °C. In the apatitic phase there was some carbonate substitution for phosphate and hydroxyl ions at 450 °C and almost solely for phosphate at 525 and 600 °C as identified by FTIR. This was accompanied by a higher hydroxyl content at 525 and 600 °C. At 450 °C a texture on the coating surface was observable by SEM that was attributable to a calcium hydroxide and calcite formation by XRD. These phases almost disappeared at 600 °C, probably due to a transformation into calcium oxide. Amorphous calcium phosphate coatings were produced by pulsed laser deposition from targets of nonstoichiometric hydroxyapatite (Ca/P = 1.70) at a low substrate temperature of 300°C. They were heated in air at different temperatures: 300, 450, 525 and 650°C. Chemical and structural analyses of these coatings were performed using X-ray diffraction (XRD), FTIR, and SEM. XRD analysis of the as-deposited and heated coatings revealed that their crystallinity improved as heat treatment temperature increased. The main phase was apatitic, with some β-tricalcium phosphate in the coatings heated at 525 and 600°C. In the apatitic phase there was some carbonate substitution for phosphate and hydroxyl ions at 450°C and almost solely for phosphate at 525 and 600°C as identified by FTIR. This was accompanied by a higher hydroxyl content at 525 and 600°C. At 450°C a texture on the coating surface was observable by SEM that was attributable to a calcium hydroxide and calcite formation by XRD. These phases almost disappeared at 600°C, probably due to a transformation into calcium oxide.