Abstract The standard molar Gibbs free energy of formation of Fe 0.540Te 0.460 was determined by measuring the vapour pressure of tellurium over the biphasic (Fe + Fe 0.540Te 0.460) alloy between 866.0 and 999.0 K using the Knudsen-effusion mass-loss technique. The vapour pressure of tellurium over the iron-rich alloy can be represented by lg( p kPa ) = 7.157 − 9860.5( K T ) ± 0.027 . Using the vapour pressure of Te 2(g) over Te(l), we calculated Δ f G m o(Fe 0.540Te 0.460, s , T)/ (kJ·mol −1) = −16.956+0.00137( T K )±0.71 . A comparative study of the stabilities of tellurides of ASTM 316 stainless-steel components has been made. The tellurium potentials required for the corrosion of 316 S.-S. due to the formation of Fe 0.540Te 0.460, Cr 0.454Te 0.546, and Ni 0.630Te 0.370 at 1000 K are also compared. It is inferred that the probability of formation of Cr 0.454Te 0.546 is the highest due to the large negative value (−33.94 kJ·mol −1) of Δ f G m o for this compound at the operating fuel-pin temperature compared with other tellurides.