Influence of powder morphology and sintering temperature on the properties of hydroxyapatite

Abstract

The effect of sintering two hydroxyapatite (HA) powders (designated HAC and HAS) of contrasting morphology, at temperatures ranging from 1000°C to 1450°C, on the phase stability of the material was investigated. Pellets were prepared by cold isostatic pressing of the powders at 200 MPa and subsequently sintering in air at a heating rate of 2°C/min. and a holding time of 2 hours. X-ray diffraction analysis revealed that decomposition of the HA was dependent on the morphology of the precursor powders. The decomposition of the HAS powder started to occur at a lower sintering temperature of 1300°C, whereas the HAC powder only decomposes at 1400°C. Both powders formed residual phases of tri-calcium phosphates and tetra-calcium phosphate due to decomposition. The possible factors controlling the decomposition mechanism of the HA powders are also discussed.