Purification of Rare Earth Metals by Solid State Electrotransport Processing

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As a part of a series of the purification of the rare earth metals by the solid state electrotransport (SSE) processing, the experimental studies were conducted. Yttrium was selected as a rare earth metal, and oxygen as the impurity.1.The SSE purification apparatus was built, which can be used for the SSE processing of the very chemically active rare earth metals.2.Oxygen content in yttrium was analyzed by the inert gas fusion infrared absorptiometric method. The most suitable conditions of the oxygen analysis were determined ; flux is Platinum, the addition>50mol% and extraction temperature=2873K.3.Oxygen in yttrium transported toward the anode by SSE processing, therefore the cathode side was purified.4.The electrotransport properties (eg.effective valence Z^*, delta(=eEZ^*/kT)) were measured. The effective valence of oxygen in yttrium increased with increasing oxygen content.delta decreased linearly with increasing temperature. The mobility of oxygen in yttrium increased with increasing temperature.5.The diffusion coefficient of oxygen in yttrium was also determined in the temperature range from 1173 to 1563 K by the SSE processing.6.From the viewpoint of the industrialization, the experimental studies were also conducted using a large scale specimen. Comparing this experimental result with the information of 4., the problems which would be encountered in the industrialization were pointed out.