| Abstract
| - The pseudo-binary Na2B4O7−[Na3AlF6−TiO2]11 system has been investigated at room temperature by meansof X-ray diffraction, IR, Raman, and UV−vis spectroscopies. Evolution of the different spectra with Na2B4O7and TiO2 contents evidenced the breaking-up of the large borate rings in favor of small borate units, thediminution of the BIV fraction, and the partial substitution of oxygen by fluorine with the formation ofoxyfluoride species. Two domains of compositions are described: a TiO2-rich region with 20−50% Na2B4O7with the lowering of boron coordination and formation of Ti(O,F)6 units and a TiO2-poor region with 60−90% Na2B4O7 where the Na3AlF6 modifier behavior is predominant. The enhanced modifier effect of [Na3AlF6−TiO2]11 in comparison with pure Na3AlF6 on the vitreous network of Na2B4O7 consists of fluorinepreference for binding to higher strength cations, Ti4+, over Al3+ and Na+ respectively, when TiO2 additionexceeds 5 wt %.
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