Crystallographic and microchemical characterization of the early stages of eutectoid decomposition in MgO-partially stabilized ZrO2

The early stages of eutectoid decomposition in ZrO2-8 mol% and 11 mol% MgO were studied by means of analytical electron microscopy. The observed reaction products at the grain boundaries were monoclinic or tetragonal ZrO2 phases and MgO precipitates of two different “cellular” morphologies. The application of energy dispersive X-ray microanalysis led to the detection of an abrupt change in the MgO content in the m-ZrO2 phase, indicating that the eutectoid decomposition in ZrO2–MgO is controlled by interface rather than volume diffusion. The crystallographic relationships between the parent phase and decomposition products were also determined.