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Phase equilibria in the NaCI–Na3AIF6-Na2B4O7-TiO2 system
Elena M Anghel, Marina Balasoiu, Stefania Zuca, Eugen Segal

As a part of the quaternary system NaCl – Na2B4O7 – Na3AlF6 – TiO2, the systems NaCl – (Na3AlF6 – TiO2)e and Na2B4O7 – (Na3AlF6 – TiO2)y (where e = 3.5 wt% TiO2 and y = 3, 3.5, 5.8, 6 and 7 wt% TiO2) were investigated by differential thermal analysis, thermogravimetry, x-ray diffraction, and infrared spectroscopy. For both systems the specific polymorphic transitions were shown, as well as the ternary eutectic transition in the case of Na2B4O7 – (Na3AlF6 – TiO2)y mixtures. Additional structural information was obtained for NaCl – (Na3AlF6 – TiO2)e mixtures by infrared spectroscopy. The shift of the infrared band positions of Na3AlF6 towards lower wave number, when TiO2 was added, could be due to the presence of titanium mainly in the form of (TiF6) octahedra. The additional thermal effect registered on differential thermal analysis curves of (Na2B4O7 – (Na3AlF6 – TiO2)y mixtures over the 10 – 30 wt% Na2B4O7 concentration range was explained in terms of the development of a solid solution.

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