Application of the constant stoichiometrygrouping concept to the Raman spectra of BaO-Al2O3-B2O3 glasses

摘要

A new approach to glass structure, involving so-called constant stoichiometry groupings (CSGs) and based on Raman spectroscopy data, has been proposed to investigate the interactions of initial oxides in melts. The vibrational spectra of glasses are interpreted as a superposition of a relatively small number of unchangeable spectral forms belonging to the CSGs. The composition dependences of the concentrations of the CSGs afford an opportunity to explain, calculate and predict the compositional dependences of the properties of binary and ternary glasses, and the existence of new crystalline compounds. The present work shows the application of the CSG concept to the barium aluminoborate (BaAB) glass system, and demonstrates that systematic data on glass properties can give some information on the phase diagram and the localisation of compounds. The compositions obtained by use of the CSG concept for glasses were found to correspond to crystal stoichiometries on the BaAB phase diagram. Furthermore, it was shown that CSG localisation corresponds to extremafor the structural thermal expansion coefficient. We have found that the minima in T_g versus composition for all series of glasses investigated coincide with the composition ranges where mixtures of CSGs occur.