The structural change of 11 mol% MgO-ZrO2 by aging has been investigated using the dilatometric, X-ray diffraction and transmission electron microscopic techniques. Above 1413 K, the cubic ZrO2 decomposed to MgO + tetragonal ZrO2 eutectoidically. Below 1413 K, two kinds of decomposition have taken place. One is the precipitation of tetragonal phase in the cubic matrix. The other is the eutectoidic decomposition to MgO + monoclinic ZrO2 . The eutectoidic temperature was estimated at 1503 K. The equilibrium and metastable phase diagrams have been discussed in the ZrO2 rich part of the MgO-ZrO2 system.
(Received September 22, 1987)
Keywords: precipitation, zirconia, decomposition, eutectoid, magnesia
* Department of Materials Processing, Faculty of Engineering, Tohoku University, Sendai 980, Japan.
** Graduate Student, Tohoku University, Sendai. Present address: Toshiba Electric Company, Kawasaki