APPLICATION OF THE SIMS METHOD IN STUDIES OF CR SEGREGATION IN CR-DOPED COO .2. DEPTH PROFILES

Surface segregation-induced depth profiles of Cr were determined for C r-doped CoO single crystals equilibrated at different temperatures (13 73-1673 K) and oxygen partial pressures (10(2)-10(5) Pa), It was shown that the shape of the depth profiles depends on both conditions of an nealing and subsequent cooling procedure, It has been observed that du ring slow cooling of specimens from the condition of segregation equil ibrium at elevated temperatures to the temperature of the experiment ( room temperature), there is substantial change of the concentration pr ofile involving desegregation of Cr (Cr diffusion from the surface to the bulk) resulting in its depletion, It has also been shown that the rate of the desegregation process (the process which results in a decr ease of surface concentration) is slower than the lattice transport ki netics of Cr in CoO. It is concluded that the desegregation is rate-co ntrolled by the decomposition of a spinel-type bidimensional surface s tructure which is formed at elevated temperatures as a result of Cr se gregation.