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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on CeF3 by Materials Project

CeF3 crystallizes in the hexagonal P6_322 space group. The structure is three-dimensional. Ce3+ is bonded in a 12-coordinate geometry to twelve F1- atoms. There are a spread of Ce–F bond distances ranging from 2.37–2.94 Å. There are three inequivalent F1- sites. In the first F1- site, F1- is bonded in a trigonal planar geometry to three equivalent Ce3+ atoms. In the second F1- site, F1- is bonded in a 1-coordinate geometry to four equivalent Ce3+ and one F1- atom. The F–F bond length is 2.54 Å. In the third F1- site, F1- is bonded to six equivalent Ce3+ and six equivalent F1- atoms to form face-sharing FCe6F6 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CeF3 by Materials Project

CeF3 crystallizes in the trigonal P-3c1 space group. The structure is three-dimensional. Ce3+ is bonded in a 9-coordinate geometry to nine F1- atoms. There are a spread of Ce–F bond distances ranging from 2.41–2.63 Å. There are three inequivalent F1- sites. In the first F1- site, F1- is bonded in a trigonal planar geometry to three equivalent Ce3+ atoms. In the second F1- site, F1- is bonded in a 3-coordinate geometry to three equivalent Ce3+ atoms. In the third F1- site, F1- is bonded in a trigonal planar geometry to three equivalent Ce3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CeF3 by Materials Project

CeF3 is Sodium arsenide structured and crystallizes in the hexagonal P6_3/mcm space group. The structure is three-dimensional. Ce3+ is bonded in a 5-coordinate geometry to eleven F1- atoms. There are a spread of Ce–F bond distances ranging from 2.40–2.71 Å. There are three inequivalent F1- sites. In the first F1- site, F1- is bonded in a trigonal planar geometry to three equivalent Ce3+ atoms. In the second F1- site, F1- is bonded in a trigonal planar geometry to three equivalent Ce3+ atoms. In the third F1- site, F1- is bonded in a 1-coordinate geometry to four equivalent Ce3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Thermal conversion in air of rare-earth fluorides to rare-earth oxyfluorides and rare-earth oxides

Phase transformations of seven different rare-earth fluorides (i.e., REF3) where RE = La, Ce, Pr, Nd, Tm, Yb, Lu at temperatures ranging from 400–1400°C in air were investigated with X-ray diffraction. All of the REF3 compounds first transformed to oxyfluorides and then to oxides, with the exception of CeF3, which transformed directly to an oxide. This study focuses on the phase transitions of REF3 to REOx by simple heat-treatment processes in air and shows plausibility to remove RE elements from fluoride salt streams from molten salt reactors through fluoride-to-oxyfluoride or fluoride-to-oxide conversion mechanisms, which will result in precipitation. This could be used to remove fission product poisons from molten salt reactor waste streams. A waste form option for the resulting REOx products is lanthanide aluminoborosilicate (LABS) glass. To demonstrate this NdF3 was converted to Nd2O3 and immobilized in a LABS glass.

oxyfluoride, molten salt reactors, fluoride salt w↗