Abstract
Thermodynamic description of the ZrO2-MgO-MnOx was derived for the first time using available experimental data on phase relations in air and protective gas atmosphere. Solid solution phases were modelled using compound energy formalism. The liquid phase was described by the modified two-sublattice model for ionic liquid. Solubility of ZrO2 was modelled in cubic spinel and MgO-MnO solid solution (halite structure) and therefore the Gibbs energies of Zr-containing endmembers were introduced. Ternary interaction parameters were introduced for halite, cubic spinel and cubic ZrO2 to reproduce the stabilization of cubic ZrO2 at temperatures below its stability in bounding systems and stabilization of cubic spinel at temperatures above its stability limit in the bounding systems. The obtained thermodynamic database was used to interpret results of differential thermal analysis.
Highlights
Phase equilibria in the ZrO2-MgO-MnOx system are of interest due to several possible applications
The calculations were performed taking into account the gas phase which thermodynamic description was accepted SGTE Substance Database (SGSUB).[30]
The phase diagrams of the ZrO2-MgO-MnOx system calculated in the present study at air oxygen partial pressure and fixed temperatures are compared with ones constructed based on experimental data[8] in Fig. 2(a), (b), (c), (d) and (e)
Summary
Phase equilibria in the ZrO2-MgO-MnOx system are of interest due to several possible applications. The other possible application of the ZrO2-MgO-MnOx system is for directionally solidified eutectic materials since both bounding systems ZrO2-MgO and ZrO2-MnOx are known to form directionally solidified eutectics.[6,7]. It was shown that relatively small additions of ZrO2 stabilize cubic spinel in the ternary system in air at temperatures exceeding its stability range in the MgO-MnOx bounding system and compositions substantially enriched by MgO. The addition of ZrO2 significantly extends the homogeneity range of halite (MgO-MnO solid solution) toward MnO solubility in air. It should be noted that cubic ZrO2-based solid solutions are stabilized in the ZrO2-MgO-MnOx system down to lower temperatures in comparison with the bounding systems both in air and inert gas atmosphere
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