Influence of various alkali and divalent metal oxides on phase transformations in NiO-doped glasses of the Li2O-Al2O3-SiO2-TiO2 system

Regularities of phase transformations in glasses of the Li2O-Al2O3-SiO2-TiO2 system doped with up to 2.5 mol% of alkali- and divalent metal oxides were studied by X-ray diffraction analysis, Raman scattering and optical spectroscopy. Ni(II) ions were used as spectral probes of phase transformations because Ni(II)-ions enter the inhomogeneous regions formed during the phase separation and crystallization, and their absorption spectra change with heat-treatment temperature reflecting formation of aluminotitanate amorphous regions, spinet nanosized crystals and beta-quartz solid solutions, consequently. It was demonstrated that the technological additives do not change the sequence of the phases' formation but accelerate the liquid phase separation and crystallization. Addition of MgO and ZnO leads to increasing the temperature range of spinel precipitation. Addition of CaO, BaO and PbO results in increasing the light scattering of prepared glass-ceramics. In selection of the technological additives for decreasing the melting temperature of glass-ceramics for optical and photonic applications the influence of the additives on the structure and optical properties of the prepared material should be considered. (C) 2011 Elsevier B.V. All rights reserved.