THE ROLE OF HPO4(2-) AND CO3(2-) IONS IN THE TRANSFORMATION OF SYNTHETIC APATITES TO BETA-CA3(PO4)2

The simultaneous effect of HPO42- and CO32- ions on the thermal decomposition of synthetic carbonated apatites to β-tricalcium phosphate has been studied. The apatites were prepared under different pH conditions and with different carbonate concentrations and were then heated with and without CaHPO4·2H2O up to 1100°C. The products were studied by infrared, Fourier transform infrared, and x-ray diffraction methods. The results showed that when HPO42- is present in the system (preparation at low pH or addition of CaHPO4), β-Ca3(PO4)2 formed below 700°C and that decomposition was slower or was prevented totally in the presence of carbonate ions. © 1990.