Phase Equilibria in the ZrO₂–MgO–MnO_x System

E-ISSN： 1551-2916|99|9|3136-3145

ISSN： 0002-7820

Source： JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Vol.99, Iss.9, 2016-09, pp. : 3136-3145

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Abstract

Phase equilibria were experimentally investigated in the MgO–MnO_x and the ZrO₂–MgO–MnO_x systems for different oxygen partial pressures by powder X‐ray diffractometry, scanning electron microscopy, and differential thermal analysis. The formation of two compositionally and structurally different β‐spinel solid solutions was observed in the MgO–MnO_x system in air in the temperature interval 1473–1713 K. Isothermal sections of the ZrO₂–MgO–MnO_x phase diagram were constructed for air conditions ( $P_{O_{2}}$ = 0.21 bar) at 1913, 1813, 1713, 1613, and 1523 K. In addition, isothermal sections at 1913 and 1523 K were constructed for $P_{O_{2}}$ = 10⁻⁴ bar. The β‐spinel and halite phases of the MgO–MnO_x system were found to dissolve up to 2 and 5 mol% ZrO₂. A continuous c‐ZrO₂ solid solution forms between the boundary ZrO₂–MnO_x and ZrO₂–MgO systems. It stabilizes in the ZrO₂–MgO–MnO_x system down to at least 1613 K in air and down to 1506 K at $P_{O_{2}}$ = 10⁻⁴ bar.