Thermal properties and thermodynamic model of lithium doped 45S5 bioglass

Shakhmatkin and Vedishcheva thermodynamic model (SV TDM) of the 45S5 Bioglass (R) doped with three different amounts of Li2O (4.1, 9.9, and 12.3 mol%) was evaluated at T = 800 K. The 55 components of SV TDM were considered, among them 12 lithium containing compounds. Different number of components with not negligible equilibrium molar amount was found for different glass compositions (9 or 10). In all glass compositions containing nonzero amount of Li2O, the four lithium compounds with not negligible equilibrium amount were identified, i.e., Li2O center dot SiO2, 3Li(2)O center dot P2O5, Li2O center dot 2CaO center dot 2SiO(2), and 2Li(2)O center dot SiO2. In the 45S5 glass composition four phosphate compounds with not negligible abundance were identified: 9Na(2)O center dot 6SiO(2)center dot 2P(2)O(5), Na2O center dot 2CaO center dot P2O5, 5Na(2)O center dot 4SiO(2)center dot P2O5, and Na2O center dot CaO center dot P2O5. In all other glasses the 3Li(2)O. P2O5 was found with not negligible abundance. Moreover, in the glass with 4.1 mol% Li2O the Na2O center dot 2CaO center dot P2O5 and 3Li(2)O center dot P2O5 compounds were found with not negligible abundance. For each studied glass the glass transition temperature, coefficient of thermal expansion of glass and metastable melt were measured by thermodilatometry. The low temperature viscosity was measured by thermomechanical analysis. The viscous flow activation energy was evaluated from the viscosity temperature dependence. The compositional dependence of measured thermal properties was analyzed by correlation analysis with the Q-distribution of silicate and phosphate units.