Solubility and thermodynamic properties of oxygen in solid molybdenum

The solubility of oxygen in solid Mo, determined in the range 1400 to 1900°C by equilibrating rods of zone-refined Mo with mixtures of Mo and MoO₂ powders, can be expressed as ln Χ_O ^α(sat) (atom fraction) = 5.86 - 27,900/T Using the known value of the free energy of formation of MoO₂, the chemical potential of oxygen in the dilute solid solution is calculated to be μ^α _O1/2μ^o _O2 = ΔG ^α _O = -10,760 + (6.92 +R ln χ^μ _O)T ± 1000 cal/g-atom oxygen The heat of solution of oxygen in Solid Mo, ΔH_Oα = -10,760 ± 3000 cal/g-atom oxygen, and the excess entropy for the interstitial solid solution ΔS_Oα(xs, i) =- 9.10 ± 1.5 cal/degree, g-atom oxygen, assuming that the oxygen atoms reside in the octahedral interstices of bcc Mo.