Structural Features of K2O-SiO2 Melts: Modeling and High-Temperature Experiments

Abstract

Despite numerous investigations, the thermodynamic properties of potassium silicates remain apparently contradictory. In situ experiments are complicated by the unstable behavior of a K2O–SiO2 melt in the region of compositions with a high potassium oxide content. In this paper, we study the structure of melts by the method of physicochemical modeling, taking into account the results of high-temperature Raman spectroscopy. To do this, the Raman spectra were curve-fitted, taking into account the second coordination sphere of silicon atoms. From the interpretation of the spectra of K2O–SiO2 glasses and melts having a K2O content of up to 55 mol.%, quantitative characteristics of the system were obtained. Since available information on the thermodynamic properties of potassium silicates is known to be contradictory, coordinated thermodynamic characteristics of potassium silicates, some of which were evaluated, were used as input data for modeling. Structural modeling of glasses and melts of the K2O–SiO2 system was carried out across a range of compositions up to 60 mol.% potassium oxide. The database of structural units of melts of the potassium silicate system, updated according to experimental data, will find practical application in chemistry, geochemistry and engineering fields.