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2007
ACL
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E.M.Anghel, P.Florian, C.Bessada, 'Structural description of Na3AlF6-Na2B4O7-TiO2 system: part I : IR and Raman study of the solidified melts', J. Phys. Chem. B 111 962-967 (2007) doi:10.1021/jp061977e
The pseudo-binary Na2B4O7-[Na3AlF6-TiO2]11 system has been investigated at room temperature by means of X-ray diffraction, IR, Raman, and UV-vis spectroscopies. Evolution of the different spectra with Na2B4O7 and TiO2 contents evidenced the breaking-up of the large borate rings in favor of small borate units, the diminution of the BIV fraction, and the partial substitution of oxygen by fluorine with the formation of oxyfluoride species. Two domains of compositions are described: a TiO2-rich region with 20-50% Na2B4O7 with 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 fluorine preference for binding to higher strength cations, Ti4+, over Al3+ and Na+ respectively, when TiO2 addition exceeds 5 wt %.
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