摘要 : A-type carbonate apatites with different CO_3 contents were obtained by heating hydroxyapatite powder in dry carbon dioxide atmosphere at 1173 K for 1 to 64 hours. The replacement of Co_3 ions lowered the crystal symmetry to hexag... 展开 A-type carbonate apatites with different CO_3 contents were obtained by heating hydroxyapatite powder in dry carbon dioxide atmosphere at 1173 K for 1 to 64 hours. The replacement of Co_3 ions lowered the crystal symmetry to hexagonal (P6_3Im) → hexagonal (p-6) → monoclinic (Pb) in that order. The a-axis parameters were linearly increased with the increase of CO_3 ions, while the b- and c-axis parameters were varied little. The lattice parameters of the A-type carbonate apatite completely replaced by CO_3 ions were refined to be a =0.9572(1), b=1.9084(1) and c =0.6877(1). The splitting of IR absorption bands attributed to a PO_4 ion also supported the lowering of crystal Symmetries 收起