Cathodic Phase Transformations During Direct Electrolytic Reduction of Nb2O5 in a CaCl2-NaCl-CaO Melt

The phase transformations during direct electrochemical reduction of Nb2O5 were investigated through constant potential electrolysis in a CaCl2-NaCl-CaO melt at 1073 K. The microstructure and phase compositions of the cathode during the reduction were determined. The mechanism of the transformations was elucidated in the view of structure. The results show Chemical reactions between CaO and Nb2O5 occurred spontaneously in the melt, forming calcium niobates with different morphology. During the electrodeoxidation, the intercalation of calcium ions into the cathode formed calcium niobates with large particle size, and then disintegrated them to much smaller ones. The CaO concentration in the CaCl2-NaCl melt can affect the morphology of final niobium product.