PREPARATION AND METALLIC REDUCTION OF RARE-EARTH HALIDES AND OXIDES
The development of techniques for the preparation of high-purity rare- earth metals is described. Rare-earth metals, excepting samarium, europium, and ytterbium, were prepared by converting their oxides to anhydrous chlorides or fluorides and reducing the rare-earth halides with active metals such as lithium or calcium. High-purity, anhydrous rare-earth chlorides were prepared by dissolving the rare-earth oxides in hydrochloric acid to form hydrated chlorides and by subsequently dehydrating the hydrated salts in the presence of ammonium chloride at temperatures ranging from 70 deg to 360 deg C while under reduced pressure (50 microns to 1 inch Hg). The chlorides were also prepared by direct chlorination of rare-earth oxide-carbon mixtures. Reaction efficiencies in excess of 95% were obtained by either method; however, purer chlorides were prepared by the aqueous ammonium chloride conversion method. Purification of yttrium chloride by high-temperature vacuum distillation proved to be an effective method of separating oxygen-bearing compounds from the chloride. Yttrium metal prepared from purified chloride contained significantly smaller amounts of oxygen (990 ppm oxygen in yttrium metal prepared fronw raw chloride and 200 ppm in that prepared from distilled chloride). Rare-earth fluorides were prepared by a solid-state reaction between the rare-earth oxides and ammonium bifluoride. This reaction was characterized by high reaction efficiencies and almost 100% conversion of the oxides to anhydrous, oxygen-free fluorides. Both the chloride and fluoride saits were reduced to metal by metallic reduction under an inert atmosphere. Rare-earth metals of greater than 99% purity were prepared by inert-atmosphere crucible-reduction techniques. Reaction efficiencies of 95 to 99% were realized by reduction cf the halides with calcium or lithium. Efforts to prepare rare-earth metals by bomb-reduction techniques were generally unsuccessful. Reactions performed in this manner were characterized by low yields and impure metal products. The application of vacuum-reduction techniques, that is, the Pidgeon process, for the preparation of saniarium and europium was not only demonstrated to be technically feasible, but it also indicated that these techniques could readily be adapted to commercial production. Yields in excess of 90% were obtained by lanthanum reductions of europium oxide at temperatures as low as 900 deg C; the purity of the europium product was greater than 99%. (auth)
- Research Organization:
- Bureau of Mines. Albany Metallurgy Research Center, Ore.
- NSA Number:
- NSA-16-003395
- OSTI ID:
- 4832372
- Report Number(s):
- BM-RI-5880
- Resource Relation:
- Other Information: Orig. Receipt Date: 31-DEC-62
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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Related Subjects
AMMONIUM COMPOUNDS
CALCIUM
CARBON
CHEMICAL REACTIONS
CHLORIDES
CHLORINATION
CONVERSION
CRUCIBLES
DISTILLATION
EFFICIENCY
EUROPIUM
EUROPIUM OXIDES
FLUORIDES
GASES
HALIDES
HIGH TEMPERATURE
HYDROCHLORIC ACID
IMPURITIES
INERT GASES
LANTHANUM
LITHIUM
METALS
OXIDES
OXYGEN COMPOUNDS
PREPARATION
PURITY
RARE EARTHS
REACTION KINETICS
REDUCTION
SAMARIUM
SEPARATION PROCESSES
SOLIDS
SOLUTIONS
VACUUM
YTTRIUM
YTTRIUM CHLORIDES