Influence of K and Mg substitutions on the synthesis and the properties of CaO-MgO-SiO2/Na2O, P2O5, CaF2 bioactive glasses

Abstract Novel glasses in CaO-MgO-SiO2 system with Na2O, P2O5, and CaF2 additives were produced by melting/quenching technique. The influence of K2O and MgO on glass structure, the thermal properties (of major importance for evaluating the crystallization mechanism), and properties related to their potential in biomedicine (bioactivity, machinability), was investigated. According to Raman spectra, K2O for Na2O substitution favors the formation of Q0 and Q1 silicate units at the expense of Q2 and Q3 ones, whereas substitution of MgO for CaO increases the Q2 and Q3 units at the expense of Q1 ones. The presence of K2O caused the increase of Tg and of the crystallization temperature as well as of the Ea of crystallization. A weaker influence on the above magnitudes was recorded in glasses with MgO substitution. The produced glasses are generally prone to 3-dimensional crystallization, display bioactivity in SBF testing, and manifest positive value of the machinability parameter n.