Quantitative Raman spectroscopy: High-temperature speciation of potassium silicate melts

In situ, high-temperature Raman spectroscopy was used to study the Qn speciation in binary potassium silicate melts. Over 300 Raman spectra in the compositional range from 20 to 38 mol% K2O were collected at temperatures between 800 and 1200 K. Quantitative information on the relative abundances of species in melts was obtained from the Raman spectra through a quantification procedure that does not require any a priori assumptions about the line shapes or external calibration of the Raman scattering efficiencies for the various Qn species. The ΔH0 associated with the speciation reaction 2Q3 = Q4 + Q2 was found to be 33.1 ± 7.3 kJ/mol.