Effects of powder stoichiometry on the sintering of β-tricalcium phosphate

The impact of weak stoichiometry variations on beta-TCP sintering behaviour was studied. beta-Tricalcium phosphate (beta-TCP) powders were synthesised by chemical precipitation through aqueous solution of diammonium phosphate and calcium nitrate. Excess or deficiency of nitrate salt leads to compositions with Ca/P ratios below or over 1.5. These powders, calcined at various temperatures (800-950 degrees C), were shaped by slip casting process and sintered at 1100 degrees C. The microstructure, phase composition, specific surface area and density of powders and sintered compacts were analysed by SEM, XRD. FTIR, BET, Archimedes methods and dilatometry. This study shows that the presence of calcium pyrophosphate or the hydroxyapatite phases affects considerably the physical characteristics of the beta-TCP powders and in particular specific surface area and consequently their sinterability. A precise determination of the beta-TCP chemical composition after synthesis allows to adapt the calcination temperature of the raw powder in order to obtain a maximum densification of the compact. The beneficial role of small quantity of HA phase inside beta-TCP powder on their sinterability was also shown in this work. (c) 2006 Elsevier Ltd. All rights reserved.