Sintering of tricalcium phosphate–fluorapatite composites by addition of alumina

Abstract The effect of alumina (Al 2 O 3 ) 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 31 P and 27 Al nuclear magnetic resonance. The composites sintering alumina additives have been tested in order to enhance their sinterability. When small amount of Al 2 O 3 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% Al 2 O 3 at 1300 °C. High temperatures were not very efficient conditions. About 1400 °C, grain growth becomes important and induces an intragranular porosity which is responsible for decrease in density. The 31 P and 27 Al MAS-NMR analysis of tricalcium phosphate–26.52 wt% fluorapatite composites sintered with Al 2 O 3 additives reveals the presence of tetrahedral P and octahedral Al sites.