Amorphous calcium phosphate materials: Formation, structure and thermal behaviour

Amorphous calcium phosphate (ACP) is essential in formation of mineralized bone and using as a bone substitute. This study presents new aspects of carbonated ACP crystallization during heat treatment. Initially synthesis end pH and drying method (80 degrees C or freeze-drying) of ACP were varied. Thermal behaviour and structure of differently obtained ACP were evaluated using DSC-TGA, heating microscopy, XRD, FT-IR. In addition, degree of crystallinity (DOC), phase composition and chemical group information were compared for as-synthesized and heat-treated (crystallization end T and 1200 degrees C) ACP. For the first time DSC-TGA and heating microscopy methods were correlated. DOC of samples dried at 80 degrees C was synthesis end pH dependent. Heat treatment without temperature hold at crystallization end T produced materials with DOC of 82-91%, thus proving efficiency of low temperature processing. Variations in drying method and synthesis end pH affect structure of the samples heat treated at crystallization end T, but not at 1200 degrees C.