A THERMODYNAMIC STUDY OF THE MOLYBDENUM OXYGEN SYSTEM

In the present work, the oxygen partial pressures corresponding to Mo/MoO2 equilibrium were measured by a solid-electrolyte galvanic cell method. The cell used can be represented as [GRAPHICS] The measurements were carried out in the temperature range of 1224 to 1584 K. The electromotive force (EMF) measured is represented by the following equation: E (mV) = 122.02 - 0.09762.T (K) +/- 2.12. The values are in good agreement with the earlier measurements. Combining these, an optimized expression for the RT In P-O2, corresponding to Mo/MoO2 equilibrium, was arrived at: RT In P-O2 (J/mole) (-580,563 +/- 916) + (173.0 +/- 0.72).T (K). This was incorporated along with the thermodynamic information of other phases in the Mo-O system to achieve a complete thermodynamic description of mainly the solid-phase region of this system by a CALPHAD approach.