Electrolytic Preparation of Lanthanide and Actinide Hexaborides Using a Molten Cryolite-base Electrolyte.
U S Pat 3 902 973 Sept 2 1975 :
Lanthanide and actinite hexaborides are prepared by fused-salt electrolysis. The electrolyte contained a major portion of cryolite and a minor portion of an alkali borate and a source compound to give the lanthanide or actinide metal. The electrolysis may be conducted in an unprotected atmosphere. The coarsely crystalline hexaboride is deposited on the cathode. The temperature is maintained from 900 deg to 1,100 deg c, preferably from 950 deg- 1,050 deg c. The current density can vary from 15 to 150 a/dm2. The cell potential is generally 2.0-5.0 V. The process may be batch or continuous. A representative melt is la2o3 7, na2b4o7 15, na3alf6 70, and na2co3 8 wt pct.
U.S. Pat. 3,902,973; Sept. 2, 1975; Chem. Abstr. 83:185,521A