| Abstract |
A series of alkali silicate glasses of molar composition 80SiO(2)-20R(2)O (R=Li, Na, K, Rb) were prepared by melting and casting and their structure has been analysed by infrared (IR) absorption and variable angle reflection spectroscopies, together with polarised Raman spectroscopy. Particular attention has been given to the frequency region below similar to 600 cm(-1), in order to correlate far IR spectra with modifying cation motions. The low frequency IR absorption bands clearly depend on the mass of the alkali cation. Kramers-Kronig analysis of the IR reflection data has been performed and the corresponding transverse optical (TO) and longitudinal optical (LO) spectra were obtained and compared with the IR reflection spectra at variable incidence angles. The extent of the TO/LO vibrational mode splitting has been correlated with the degree of modification of the glass network. The Raman spectra were interpreted essentially on the basis of vibrations of Q(3) units. |
