Most hydroxyapatite coated implants produced by plasma spraying contain the amorphous phase which affects the longevity of the coatings. It is thus necessary to measure, locate and quantify this in the microstructure for quality control and analysis of retrieved implants. Several methods are available both for micro-characterization and analysis on the calcium phosphate coatings. These techniques include microscopy (optical, secondary electron and cathodoluminescence), spectroscopy (infra-red and Raman), thermal analysis and X-ray diffraction. The amorphous phase produces peak broadening in infra-red, however the interpretation is complex due to the contribution of residual stresses. Raman spectroscopy yields an individual peak located at 950 cm-'. Crystallization events in thermal analysis indicate that the chemical composition of the amorphous phase may be hydroxyl rich or hydroxyl depleted. The most useful of these techniques is microscopy where the location, distribution, size and quantity of these regions can be readily ascertained. The information from these techniques will be discussed to reveal the nature and facilitate identification of the amorphous phase.
Bioceramics: vol. 11: Proceedings of the 11th International Symposium on Ceramics in Medicine, New York City, New York, United States, 05-08 November 1998 / Racquel Zapanta LeGeros and John P. LeGeros (eds.),