Fabrication and characterization of beta-type tricalcium phosphate sintered body with phosphorus/sulphur-complex cations

The crystal structure of β-tricalcium phosphate (β-TCP), which is used as a bone replacement material, is known to have five crystallographically distinct positions for the Ca atom and three distinct positions for the P atom. In this paper, we have successfully synthesized a new β-type tricalcium phosphate (Na-β-TCP/S) with phosphorus/sulfur-complex cations by solid state reaction method. This was achieved by using Ca20Na2(PO4)14 (Na-β-TCP) as a starting material, adjusting the Ca(4) site occupied by Na atoms to become vacancies, and simultaneously adjusting the same moles of S atoms to the P(1) site. The obtained sintered bodies became dense with increasing the sintering temperature. The grain growth of the sintered bodies was inhibited with increasing sulfur content. Although the solubility of Na-β-TCP was about half of that of β-TCP, the solubility of Na-β-TCP/S powder samples slightly increased with increasing sulfur content. These results indicate that Na-β-TCP/S can be prepared by controlling not only the amounts of vacancies in the structure but also the sinterability and solubility of Na-β-TCP/S due to the substitution of phosphorus and sulfur, and that Na-β-TCP/S has potential as a new β-TCP material for bioceramics.