“…Since the late 1960s, researchers have recognized and investigated the use of zirconia solid electrolyte for metals production and refining [14][15][16][17][18]; however, limited progress was achieved due to the poor stability of the zirconia membrane, low current density, and lack of an appropriate current collector assembly. A decade ago, Pal's pioneering work on new molten salt compositions increased solubility of many oxides, e.g., CaF 2 -MgF 2 eutectic molten salt dissolves *10 wt% MgO, decreased zirconia corrosion rate, and has generated new interest in commercialization of the process for metals production [19,20]. The SOM process has been applied to reduce various metal oxides or oxide compounds to the respective metals or alloys, including Mg [19,[21][22][23][24][25][26], Al [27], Ti [28], Ca [29,30], Fe [22], Cu [31], Ta [20], Cr [20], Nb [20,32], Yb [33], Nd, Pr, Dy, Si [34], CeNi 5 , and La x Ce 1-x Ni 5 [35], Ti-Fe alloy [36,37], Ti-Si intermetallics [38,39].…”