The role of variation of the stabilizing magnesium oxide dopant on phase transformations in the composition of ZrO2 – CeO2 ceramics

Abstract

The aim of this work is to determine the role of the addition of a stabilizing magnesium oxide dopant to the composition of composite ZrO₂ – CeO₂ ceramics in changing the kinetics of phase transformations that occur during high-temperature sintering of ceramics depending on the variation in the concentration of the dopant. According to the assessment of the microstructural features of ZrO₂ – CeO₂ ceramics, it was found that the addition of MgO in low concentrations leads to the formation of finely dispersed grains of a globular shape that are tightly packed, while an increase in the concentration of MgO above 0.05 M leads to an enlargement of the grains and a change in their shape from globular to polyhedral with the formation of MgO inclusions, the presence of which is due to exceeding the solubility limit of magnesium oxide in the ZrO₂ – CeO₂ matrix. It has been established that variation in the MgO content allows for effective control of the morphology of ZrO₂ – CeO₂ ceramics from a loose porous structure to a dense fine-grained heterogeneous system with controlled grain size, high defectivity and developed intergranular boundaries. Using X-ray phase analysis methods, it was established that the introduction of MgO leads to a restructuring of the phase composition: from the initial two-phase state to a single-phase cubic structure at 0.01 M MgO and the subsequent formation of a mixture of two cubic and tetragonal phases at higher concentrations with the dominance of the cubic phase in the composition.