High-resolution transmission electron microscopy and electron-energy-loss spectroscopy study of the phase Mg2Zr5O12 in MgO-partially stabilized zirconia

The δ phase, with composition MgZrO, has a marked effect on the thermomechanical properties of magnesia partially stabilized zirconia (MgO-PSZ). High resolution transmission electron microscopy and electron-energy-loss spectroscopy (EELS) were used to study the δ phase formed in MgO-PSZ sample during subeutectoid ageing. It was found that the δ phase, which has a higher MgO content than that of the matrix as confirmed by EELS analysis, can only nucleate at the site where two tetragonal precipitates impinged. Strain was developed around the interface between the δ phase and the tetragonal precipitate. The diameters of the δ-phase microdomains range from about 20 to 70 nm after a 2 h subeutectoid ageing treatment