The study of the system Na3AlF6–FeF3

Abstract Different techniques are used to understand the Na 3 AlF 6 –FeF 3 system behavior. Rietveld's structure refinement analysis is successfully applied to determine the lattice parameters as well as relative phase abundance of individual phases in the system Na 3 AlF 6 –FeF 3 . The results confirm the presence of Na 3 (Al x Fe y )F 6 and Na 5 (Al x Fe y ) 3 F 14 ( x  +  y  = 1) solid solutions, depending on the amount of FeF 3 in the system. The system with 25 mol% FeF 3 contains crystalline phases in weight ratio: 64.8 ± 2.8% of Na 3 (Al x Fe y )F 6 and 35.2 ± 2.7% of Na 5 (Al x Fe y ) 3 F 14 , 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 NaAlF 4 is the only vapor species, generating in the melted system.