Crystallographic characteristics of plasma-sprayed calcium phosphate coatings on Ti-6Al-4V

The purpose of this study was to investigate the crystallographic character istics of 3 sets of plasma-sprayed hydroxyapatite (HA) coatings prepared wi th different degrees of crystallinity on Ti-6Al-4V substrates. X-ray diffra ction analyses were performed on the coatings to determine mean percent cry stallinity, calcium phosphate phases present, average crystallite size, and residual strain. The mean percent crystallinity for the 3 sets of coatings ranged from 49 to 60%. The coatings that achieved the highest crystallinit y consisted almost entirely of HA. As the coating crystallinity decreased, increasing amounts of alpha- and beta-tricalcium phosphate and tetracalcium phosphate were detected. The mean HA crystallite size for the 3 sets of co atings ranged from 0.02 to 0.05 mu m. Differences in mean interplanar spaci ng for selected crystallographic planes of HA, compared with the pure ICDD (International Center for Diffraction Data) powder standards, implied that the coatings were in an uneven stale of tensile strain.