The eutectic mixtures (mol.%) 40NaF-60KF and 46.5LiF-11.5NaF-42KF were prepared with the following chemicals: lithium fluoride LiF (mass fraction of LiF 99.0%) (CJSC VECTON), sodium fluoride NaF (mass fraction of LiF 99.0%) (LLC “GRANCHIM”), potassium fluoride acidic KF‧HF (mass fraction of KF‧HF 99-101%) (LLC “GRANCHIM”).
The mixtures were prepared by direct fusion of the components in a glassy carbon crucible. KF·HF was used instead of hygroscopic KF. KF·HF decomposes at 673–773 K; the released HF prevents the hydrolysis of salts and simultaneously fluorinates oxygen-containing impurities. The mixture was kept at 923 K for at least 2 h. After cooling, the sample was transferred to a glovebox with an inert argon atmosphere. The preparation technique is described in detail elsewhere [25 (link)]. The contents of LiF, NaF and KF in the prepared sample were confirmed by the elemental chemical analysis (Li, Na, K) carried out using ICP-OES (iCAP 6300 Duo, Thermo Scientific, Waltham, MA, USA).
The neodymium trifluoride (NdF3) was prepared by hydrofluorination of Nd2O3 according to technique described in [25 (link)]. The XRD confirmed the presence of a single hexagonal phase of NdF3. Analysis of the oxygen content using the oxygen analyzer LECO OH836 indicated that its content in the prepared NdF3 does not exceed 0.04 wt%.
The mixtures were prepared by direct fusion of the components in a glassy carbon crucible. KF·HF was used instead of hygroscopic KF. KF·HF decomposes at 673–773 K; the released HF prevents the hydrolysis of salts and simultaneously fluorinates oxygen-containing impurities. The mixture was kept at 923 K for at least 2 h. After cooling, the sample was transferred to a glovebox with an inert argon atmosphere. The preparation technique is described in detail elsewhere [25 (link)]. The contents of LiF, NaF and KF in the prepared sample were confirmed by the elemental chemical analysis (Li, Na, K) carried out using ICP-OES (iCAP 6300 Duo, Thermo Scientific, Waltham, MA, USA).
The neodymium trifluoride (NdF3) was prepared by hydrofluorination of Nd2O3 according to technique described in [25 (link)]. The XRD confirmed the presence of a single hexagonal phase of NdF3. Analysis of the oxygen content using the oxygen analyzer LECO OH836 indicated that its content in the prepared NdF3 does not exceed 0.04 wt%.
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