Structure and properties of bioactive eutectic glasses based on the Ca3(PO4)2–CaSiO3–CaMg(SiO3)2 system

Taking into account the phase equilibrium relationships within the Ca3(PO4)2-CaSiO3-CaMg(SiO3)2 ternary system, three bioactive glasses with a eutectic composition and analogous amounts of Ca3(PO4)2 (∼40 wt.%) have been prepared. The structure of the glasses was investigated by 31P and 29Si magic angle spinning nuclear magnetic resonance (MAS-NMR) spectroscopy. The glasses exhibited thermal expansion coefficients (50-600 °C) of 11.8-13.3×10(-6) °C(-1), a glass transition temperature of 790-720 °C and a softening temperature of 811-750 °C. The mechanical properties of the glasses were as follows: bending strength ∼100 MPa, Young's modulus 94-83 GPa, Vickers microhardness 7.1-4.1 GPa and toughness 0.8 MPa m1/2. The bioactive properties were discussed in terms of their structure deduced by MAS-NMR spectroscopy and the field strength of the network modifiers (Mg2+ and Ca2+). A knowledge of the glass structure was important in predicting its bioactivity.