Physicochemical characterization of hydroxyapatite (Ha) powders and their composites (Z ha) using synchrotron radiation

Calcium hydroxyapatite (HA), Ca5(PO4)3 OH is the main inorganic compound of human bones and teeth. The utilization of synthetic powders in dental and medical implants has increased in the recent days. These powders can be obtained by precipitation methods from very basic solutions (pH > 10)[1] and sintered above 8000 C [2]. The X-ray diffraction (XRD) is one of the most important technique used in the characterization of HA compounds. Although a wealth of information can be obtained from XRD analyses alone, such as identify, purity, crystallinity, approximate size and shape, and lattice parameters, the combination of XRD and other types of analyses such as IR, chemical analyses, TEM and TGA gives an even more comprehensive picture of the physicochemical properties of synthetic HA powders. Purity, composition, particle size of samples and sintering conditions affect the type and amount of other calcium phosphate phases (TCP, TTCP) and/or other calcium compounds (Ca O) which can be present with the HA and ZHA phases. Through using synchrotron radiation at the LNLS, this work suggests performing experimental measurements in samples of synthetic HA and zirconia - HA composites (ZHA) powders and ceramics with the aim to determine the purity (whether single or multiphasic), crystallinity of HA and ZHA phases, the lattice parameters of HA in order to compare with results already reported. (author)