The study of the system Na3AlF6–FeF3

Different techniques are used to understand the Na3AlF6–FeF3 system behavior. Rietveldʹs structure refinement analysis is successfully applied to determine the lattice parameters as well as relative phase abundance of individual phases in the system Na3AlF6–FeF3. The results confirm the presence of Na3(AlxFey)F6 and Na5(AlxFey)3F14 (x + y = 1) solid solutions, depending on the amount of FeF3 in the system. The system with 25 mol% FeF3 contains crystalline phases in weight ratio: 64.8 ± 2.8% of Na3(AlxFey)F6 and 35.2 ± 2.7% of Na5(AlxFey)3F14, respectively. In the first mentioned solution, the molar ratio of Al/Fe is 92.8/7.2 and 77.4/22.6 in second one. Weight loss measurements suggest that some new volatile products are emitted from the melt. MAS NMR investigations of the condensate exclude the presence of iron containing fluorides in the condensed sample and confirm that NaAlF4 is the only vapor species, generating in the melted system.