A directionally solidified eutectic (DSE) of MnO-ZrO2 has been investi
gated using a variety of electron optical techniques. It is found that
considerable MnO goes into ZrO2 to form a substitutional solid soluti
on. About 14 wt% of MnO is soluble in ZrO2 close to the eutectic tempe
rature. The solubility of ZrO2 in MnO, however, is quite low, less tha
n 0.50 wt%. Electron diffraction experiments indicate that ZrO2 (MnO)
has the cubic fluorite structure. Diffuse scattering, similar to other
cubic zirconias (e.g., CaO, MgO stabilized zirconia), is also observe
d in manganese-stabilized zirconia. Diffuse scattering indicates the p
resence of oxygen vacancies and thus confirms the defect nature of the
fluorite structure. Electron energy loss spectrometry (EELS) fine str
ucture analysis of the Mn L23 edge provided clear evidence that Mn is
present as Mn2+ in Mn-stabilized cubic ZrO2.