Electro-deoxidation of hafnium dioxide and niobia-doped hafnium dioxide in molten calcium chloride

This paper investigates the capability of the FFC-Cambridge process of producing metallic hafnium powder that can meet commercial standards. The results show that the reduction in the core of the pellet is hindered in an intermediate step associated with the formation of CaHfO3. Doping the initial hafnium oxide with niobium oxides in the initial pellet prevents this blocking. The charge passed is much higher than that observed with undoped HfO2. The powder obtained after 36 h of electro-deoxidation is an Hf–Nb alloy cubes with 0.8 wt.% oxygen content and 5–20 μm size.

► We studied the electro-deoxidation of pure and niobium doped hafnium dioxide.
► The reduction of pure HfO2 was blocked in the core of the pellet associated with the formation of long-ordered CaHfO3 crystals.
► Doping the initial precursor with niobium ions increased the oxygen ion conductivity of CaHfO3.
► Cubes of Hf–Nb alloy powder was produced with 0.8 wt.% oxygen content and 5–20 μm size.