Reaction between cerium trifluoride and elemental fluorine

Abstract

Reactions between cerium trifluoride and elemental fluorine have been examined by means of the kinetic and crystallographic method. The reactions were performed at 503–573 K under fluorine pressures of 6.7–26.7 kPa for reaction time up to 3 h. Two kinds of CeF 4 were synthesized by controlling the reaction condition. One is the metastable CeF 4-I synthesized at 523–538 K which returns to CeF 3 to release elemental fluorine, and the other is the stable CeF 4-II obtained at temperatures higher than ca. 540 K, which never returns to CeF 3. X-ray diffraction–Rietveld analysis revealed that the structure of CeF 4-I and CeF 4-II were monoclinic structure ( C12/ c1, Z=12, CeF 4-I/CeF 4-II: a 0, 1.26 nm/1.25; b 0, 1.06/1.05; c 0, 0.82/0.82; β, 126.1/126.3°; cell volume, 8.91×10 −28/8.78×10 −28 m 3) and the cell volume of the CeF 4-I was 1.4% larger than that of the CeF 4-II. Bond lengths between Ce and F in CeF 4-I were somewhat longer than those in CeF 4-II. When CeF 4 and NaCl were put separately in the reaction container, CeF 4-I changed to CeF 3 with converting NaCl to NaF, however, CeF 4-II never reacted with NaCl.