Bioactive ceramics prepared by sintering and crystallization of calcium phosphate invert glasses

Novel glass–ceramics were synthesized via sintering and crystallization by heating powder compacts of SiO2-free calcium phosphate invert glasses of 60CaO • 30P2O5 • 7Na2O • 3TiO2 or 60CaO • 30P2O5 • 7Na2O • 3MgO at 800–850°C in air. The glass–ceramics were relatively dense materials consisting of crystalline phases such as β-Ca3(PO4)2 and β-Ca2P2O7 with glassy phases. The compacts were densified by the viscous flow of the glassy phases while heating. By soaking in simulated body fluid at 37°C, a calcium phosphate phase was formed newly on the surface of the glass–ceramic derived from 60CaO • 30P2O5 • 7Na2O • 3TiO2 glass, while the phase was not formed on that derived from 60CaO • 30P2O5 • 7Na2O • 3MgO glass: the former was implied to show bioactivity. Composition of the glassy phase as the matrix varies with the additives such as TiO2 and MgO, and the chemical properties of the phase influence the bioactivity of the glass–ceramics. The glass–ceramic derived from 60CaO • 30P2O5 • 7Na2O • 3TiO2 glass has relatively high fracture toughness of KIC≈2 MPa m0.5 and bending strength of 100–120 MPa.