It was shown that only individual cerium and manganese oxides exist over th
e subsolidus region of the Ce-Mn-O system in air. This conclusion was based
on an X-ray phase analysis of the CeMnOn, Ce0.95Mn0.05Om. and Mn1.95Ce0.05
Ok ceramics, which were prepared at 800, 1000, and 1400 degrees C in air an
d were cooled in various modes. Elements of the diagram of the state for th
e Ce-Mn-O system were constructed.