Solids and Liquids in the NaF–AlF 3 –Al 2 O 3 System: A High‐Temperature NMR Study

Aluminofluoride and oxyfluoride melts are essential in the electrolytic smelting of aluminum, as the precursors of fluoride glasses, and as analogue systems for molten silicates. In these systems, the quantification of the abundances of structural species is crucial in the understanding of both thermodynamic and transport properties. 27 Al NMR spectroscopy at high temperatures can provide important constraints on speciation and coordination number in aluminofluoride liquids, as well as structural and dynamical changes in the crystalline fluorides. We present results on a series of solids and liquids in the NaF–AIF 3 –Al 2 O 3 system. These illustrate the dramatic effects of composition and temperature on liquid structure and suggest that most Al cations are four‐ or six‐coordinated, with a relatively low abundance of five‐coordinated sites.