Preparation of Niobium Metal Powder by Two-Stage Magnesium Vapor Reduction of Niobium Pentoxide

Table 1

Free energy of formation of some oxides at 298 K [15].

Metal oxides	Δ𝐺^∘298 (kJ/g-atom of O)
MoO3	−229
FeO	−245
WO3	−254.1
Nb2O5	−353.6
Ta2O5	−390
MgO	−568.4
CaO	−597.7
Al2O3	−526.7