Study On Preparation Of Extra-Low-Oxygen Rare-Earth Metal Yttrium By Ca-CaCl₂ Fused-Salt Methodand Electrochemistry Purification Method

In this paper, the research that the extra-low-oxygen rare-earth metal Yttrium is prepared by Ca-CaCl₂ fused-salt method and electrochemistry purification method is mainly developed. The low-oxygen rare-earth metals yttrium is obtained by using the reaction with chemically active calcium dissolved in CaCl₂ and decreasing the activity of the by-product CaO in high-temprature resistance furnace use of Ca-CaCl₂ fused-salt method. We have found optimal flux content is 40g, optimal deoxidation time is 7 days, optimal deoxidation temperature is 950℃ via studying different flux content, different material crucible, different deoxidation time, different deoxidation temperature and other technologcial conditions. Pieces of yttrium are deoxidized to 0.17wt% oxygen content at lowest by use of tantaium crucible. Removal ratio of oxygen reaches 73%.The Ca-CaCl₂ fused-salt method compared with other methods has some characters of simple experiment equipment and technics, high deoxidation ratio, and easy realization industrialization. It is expect to induce mass-produce.In this paper, basic principle and thermodynamic process of the electrochemical deoxidation purified rare earth metal yttrium are firstly demonstrated. We get thorough theory mechanism analysis on physical and chemical question of electrochemical purification method and expatiate its validity and applicability from commonly principle and thermodynamic theory. The Method can make deoxidation extreme limit lower infinitely via qualitative analysis in theory, only theelectrolysis technologcial conditions are fit. Deoxidation time as to the regular metals yttrium in shape is t = (d2I n2D)\n[(4c01nc)sin7aId]. Choice of electrolysis conditions affects raw materialconsumption, deoxidation effect, deoxidation speed, experiment favoring degree and so on.The electrochemistry purification method compared with the Ca-CaCb fused-salt method possesses more merit that include lower deoxidation limit, shorter reaction time and smaller pollution. It improves on the Ca-CaCb fused-salt method. The electrochemistry purification method should be a manipulable and effective purification method. It possesses capacious market foreground. It is important that this research can improve product quality, enlarge product quantity of rare-earth metal, and transform rare-earth resource predominance into economic predominance in our municipality.