THE STRUCTURE OF TI SILICATE-GLASSES BY MICRO-RAMAN SPECTROSCOPY

Micro-Raman spectra have been obtained for glasses prepared along the TiO2-SiO2, Na2SiO3-TiO2, and CaSiO3-TiO2 joins, and for the compounds fresnoite (Ba2TiSi2O8), barium titanate (Ba2TiO4), rutile and anatase, The spectra do not indicate the presence of 6-fold coordinated titani um (Ti-[6]) except where cryptocrystalline anatase is present. Ti is 4 -fold coordinated (Ti-[4]) in all glass systems investigated at low Ti O2 contents. However, comparison of the spectra of the glasses with sp ectra of crystalline fresnoite (Ti-[5]), glass of fresnoite compositio n, and beta-Ba2TiO4 (Ti-[4]) indicates that, at high TiO2 contents, th e alkali-containing glasses have Ti predominantly as Ti-[5]. Titanium in the alkaline-earth-containing glasses appears to be a mixture of bo th Ti-[4] and Ti-[5]. A structural reorganization of the network occur s in both the alkali- and alkaline-earth-containing glasses at around 10 mol% TiO2, and this may be associated with the formation of 5-fold coordinated titanium (Ti-[5]).