Sintering of tricalcium phosphate-fluorapatite composites by addition of alumina

The effect of alumina (Al2O3) addition on the densification of tricalcium phosphate-26.52 wt% fluorapatite composites was investigated. The sintering behaviour was investigated using X-ray diffraction, scanning electron microscopy and by analysis using P-31 and Al-27 nuclear magnetic resonance. The composites sintering alumina additives have been tested in order to enhance their sinterability. When small amount of Al2O3 was added, densification of the tricalcium phosphate-26.52 wt% fluorapatite composites was markedly enhanced. The densification of the pure tricalcium phosphate-26.52 wt% fluorapatite composites was about 87%, whereas it reached 91% with 2.5 wt% Al2O3 at 1300 degrees C. High temperatures were not very efficient conditions. About 1400 degrees C, grain growth becomes important and induces an intragranular porosity which is responsible for decrease in density. The P-31 and Al-27 MAS-NMR analysis of tricalcium phosphate-26.52 wt% fluorapatite composites sintered with Al2O3 additives reveals the presence of tetrahedral P and octahedral Al sites. (C) 2007 Elsevier Ltd and Techna Group S.r.l. All rights reserved.