Influence of MgO (CaO) on the structure of silicate-phosphate glasses

Abstract

Abstract Thermal and structural properties of model silicate-phosphate glasses containing the different amounts of the glass network modifiers, i.e. Mg2+ and Ca2+ were studied. To explain the changes of the parameters characterizing the glass transition effect (Tg, Δcp) and the crystallization process (Tc, ΔH) depending on the cations modifiers additions, analysis of the bonds and chemical interactions of atoms in the structure of glasses was used. 31P MAS-NMR spectra of SiO2–P2O5–MgO(CaO)–K2O glasses show that the phosphate complexes are mono- and diphosphate. It has been found that increasing amounts of Mg2+ or Ca2+ cations in the structure of glasses causes the reduction of the degree of polymerization of the phosphate framework (Q1→Q0). The influence of increasing of modifiers in the structure of silicate- phosphate glasses on the number of non-bridging oxygens per SiO4 tetrahedron and density of glasses was presented.