Experimental Investigation of Phase Equilibria in the ZrO2-TiO2-MgO System

Phase equilibria in the ZrO2-TiO2-MgO system are studied experimentally using X-ray diffraction (XRD), scanning electron microscopy combined with dispersive X-ray spectrometry (SEM/EDX), and differential thermal analysis (DTA). Based on the obtained experimental data, isothermal sections of the ZrO2-TiO2-MgO system at temperatures 1530, 1680, and 1880 K are established. Wide extension of stability of Zr1-xMgxO2-x phase with fluorite structure (C ZrO2) into ternary system is revealed. Very limited solubility of MgO is found in beta-(ZrxTi1-x)(2)O-4 and tetragonal (Zr1-xTix)O-2 phase (T ZrO2), while more substantial solubility of ZrO2 is found in the intermediate compounds of the TiO2-MgO system (Mg2TiO4, MgTiO3, and MgTi2O5). Low temperature ternary compound similar to delta-phase Y4Zr3O12 is revealed at 1530 K. Differential thermal analysis indicated that this delta-phase is stable up to 1664 K. Temperatures and compositions of three eutectic reactions are experimentally measured by DTA and ex situ analysis of the sample microstructures after melting using SEM/EDX.