Influence of Carbonate on Sintering of Apatites

Abstract

Sintering of carbonate apatite, prepared at 100°C and pH 9.0 for 3 days, was studied by thermal analysis, x-ray diffraction, and infrared spectroscopy. The sintering temperature, at which the linear thermal shrinkage of isostatically compacted specimens increased sharply, decreased in proportion to the amount of carbonate initially present in the apatite. For example, specimens with over 8 wt% carbonate could be sintered at a temperature (650°C) which was nearly 400°C lower than that needed for sintering a specimen with no carbonate. Amounts of carbonate lost at the end of sintering, estimated chemically and by infra-red specroscopy, were approximately equal to sample weight losses estimated thermogravimetrically