Deoxidaton of Rare Earth Metals by Halide Flux Treatmwent

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1.Preliminary Experiments by Various Halide FluxesPreliminary deoxidation experiments were conducted by using several kind of halide fluxes. Based on the above results, effect of used fluxes on deoxidation ability was investigated and effectiveness of this method was confirmed.2.REF_3 - RE-oxide (RE=Nd, Pr) Quasi-binary EquilibriumREF_3 powder and a RE-oxide pellet were charged in a graphite crucible and heated at 1723 K under argon atmosphere for a scheduled time period. Then, the crucible was pulled out from the furnace and quenched rapidly by jetting helium gas. Two phases, consisting of the melted part and the solid part, were observed in both experiments and the both were subjected to X-my diffraction analysis. The NdOF or PrOF peaks are detected in the both parts.3.RE - REF_3 - RE_20_3 Quasi-ternary SystemAs the REOF phases were identified, new sets of experiments were conducted to determine the RE - REF_3 - REOF quasi-ternary equilibrium. Using those results and the partial phase diagrams of the RE-O system, phase diagrams of the RE - REF_3 - RE_20_3 quasi-ternary system at 1723 K were established. Based on the phase diagrams, deoxidation reactions on the both rare earth metals were estimated.4.Deoxidation ExperimentsThe deoxidation experiments using NdF_3 or PrF_3 as a halide flux were performed in order to confirm the estimated deoxidation reactions. Oxygen content can be successfully lowered by the halide flux treatment. Therefore, the halide flux treatment is not only simple process but also effective deoxidation method.