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Investigation of TiO2SiO2 glasses by X-ray absorption spectroscopy

1983; Elsevier BV; Volume: 55; Issue: 1 Linguagem: Inglês

10.1016/0022-3093(83)90005-4

1873-4812

R.B. Greegor, Farrel W. Lytle, D. R. Sandstrom, Joe Wong, Peter C. Schultz,

X-ray Spectroscopy and Fluorescence Analysis

The coordination and nearest-neighbor bond distances of Ti in a series of TiO2SiO2 glasses have been quantitatively determined using a combination of XANES and EXAFS measurements about the Ti K-edge at 4966 eV. The glasses covering the range 0.012 to 14.7 wt% TiO2 were prepared by flame hydrolysis of predetermined mixtures of SiCl4 and TiCl4 vapors. At TiO2 concentrations below ∼0.05 wt%, Ti is found in a rutile-like octahedral coordination. With increased TiO2 content in the glass, a two-site model applies, in which Ti is found predominately in a fourfold site. About ∼9 wt% TiO2, t6he sixfold/fourfold ratio increases appreciably and eventually at ∼15 wt% TiO2, crystalline TiO2 segregates out as a second phase. The average TiOSi bond angle in these glasses was estimated to be ∼159 ° which is slightly larger than the most probable value of 152 degrees for SiOSi in vitreous SiO2. Within the accuracy of the edge shift measurements all Ti in the glass is in 4+ valence. Finally, various physical properties such as density, optical transparency and thermal expansion are correlated in light of the new structural data for this interesting binary silicate glass system.