Glass transition effect in liquation silicate–borate–phosphate glasses

Glass transformation effect of liquation glasses from the SiO2–B2O3–P2O5–K2O–MgO–CaO system was studied by DSC, SEM–EDS and 31P, 29Si and 11B MAS NMR spectroscopy methods. The relation between the B2O3 content in the analysed glasses and phase separation phenomenon, structure and glass transition effects was discussed. It was shown that increasing content of B2O3 causes the formation of P–O–BIII, P–O–BIV and Si–O–BIII and Si–O–BIV bonds which results in the appearance of liquation in analysed glasses. Simultaneously, double glass transition effect was observed with gradual decrease of Tg and Ea values. The observed relations were explained using crystalochemical parameters (iG, L) of chemical bonds present in the structure of analysed glasses.