Raman spectroscopy study of phase transformations in titania-containing lithium aluminosilicate glasses doped with CoO

The influence of small additions of CoO (0.05–2.0 mol%) on phase decomposition and further crystallization in glasses of the Li2O–Al2O3–SiO2–TiO2 system were studied by comparison of variations in corresponding Raman scattering spectra, optical absorption spectra and X-ray diffraction patterns. It is found out that at early stages of phase decomposition at heat-treatment temperatures of 660–700 °C, cobalt oxide enters the alurninotitanate phase, increases temperature range of its existence and influences the kinetics of formation of crystalline phases with anatase and anosovite structure precipitated in this phase upon heat-treatment. Upon heat-treatments at higher temperatures (720–750 °C), crystallization of aluminocobalt spinel and of small amounts of cobalt titanate is revealed. Addition of CoO facilitates crystallization of β-eucryptite solid solution with β-quartz structure, which takes place at the same temperatures. With increasing heat-treatment temperature, anosovite, spinel, and cobalt titanate are decomposed. At 950 °C, a part of TiO2 precipitates in the form of aluminum titanate, tialite, which leads to slowing down the crystallization of anatase.