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2013 |
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Structure of M2O–SiO2 (M = Li, Na) melts as a function of composition: in situ Raman spectroscopic study vs thermodynamic simulation results Koroleva O.N. Institute of mineralogy UrB RAS, Russia, Miass
The structure of x%M2O·(100-x)%SiO2 glasses and melts x ≤ 67 was studied by in-situ Raman spectroscopy at temperatures from 293 to 1462 K. The curve-fitting procedure was applied for data analysis taking into account the second coordination sphere of Si atoms. To obtain a correct interpretation of all bands in Raman spectra, additional types of structural unites Qn’ were introduced into description of glasses and melts structure. The conversion coefficients from characteristic Raman bands to concentrations of corresponding structural units an allowed to determine Qn-abundance in sodium and lithium silicate melts. From these data the dependence of the equilibrium constants kn of the reactions 2Qn ↔ Qn-1 + Qn+1 was determined. High-temperature Raman spectroscopy data were used for coordination of thermodynamic database of silicate melts. Physicochemical models of sodium and lithium silicate melts in the region from 0 to 67 mol. % M2O were constrained. The formed models showed quantitative estimation of component changes in melts vs. temperature and composition and a good agreement with experimental data. The work was financially supported by the Russian Foundation for Basic Research (project ¹ 12-05-00294), FTP ¹ 14.Â37.21.1259 and the Grant of Russian Federation President. | ||||
