X-Ray Structural Analysis of Molten LiF-KF(1:1) and LiF-NaF(3:2) Mixtures

Abstract

The structures of molten LiF-KF (mole ratio 1:1) mixture at 545°C and LiF-NaF (3:2)mixture at 690°C were investigated by an X-ray diffraction analysis. In the LiF-KF (1:1)system, the nearest neighbour distances and coordination numbers of unlike ion pairs were 1.85 A and 3.0 for Li⁺-F^- ion pair and 2.70 A and 4.1 for K⁺-F^- ion pair, respectively, which were found to be nearly equal to those analyzed in each pure melt. In the LiF-NaF (3:2) system, the nearest neighbour distances and coordination numbers of unlike ion pairs analyzed were 1.84 A and 3.0 for Li⁺-F^- ion pair and 2.20 A and 3.8 for Na⁺-F^- ion pair, respectively, which were almost the same as those determined in each pure melt. These results imply that the nearest neighbour structures of unlike ion pairs are similar to those of the constituent salts, i. e., they ar e unaltered by mixing process of the two fluoride melts.