Electrochemical Preparation of DyFe2 Alloy from the Solid Mixture of Dy2O3 and Fe2O3 in Molten CaCl2

Abstract

The mixed oxide pellet was prepared by pressing the mixture of Dy2O3+Fe2O3+5%wt PVB+25%wt carbon powders (Dy:Fe = 1:2) under 15 MPa, then a porous cathode pellet was obtained by sintering in air in the range of 800∼1200°C. The cathode pellet sintered in air for 2 h at 1200°C has composed of Fe2O3 and Dy3Fe5O12 phases with a porous structure. DyFe2 alloy was successfully obtained through direct electrochemical reduction of the cathode pellet sintered at 1200°C at 3.2 V in molten CaCl2 at 900°C for 10 h. The necessary conditions for obtaining the alloys are as follows: (1) high enough voltage (3.2 V); (2) formation of Dy3Fe5O12; (3) 10 h electrolysis time. By combining cyclic voltammograms with XRD results, the electrochemical reduction processes of the cathode pellet were proposed as following: The reduction of Fe2O3 to Fe as well as Dy3Fe5O12 to Fe and Dy2O3 occurred first, followed by the reduction of Dy2O3 on the produced Fe to form DyFe3, and then Dy2O3 reduction on DyFe3 to form DyFe2 alloy phases.