Investigation of Grain‐Boundary Segregation in Ceramic Oxides by Analytical Scanning Transmission Electron Microscopy

Abstract

Analytical scanning transmission electron microscopy (AEM) was used to study grain‐boundary solute segregation in the systems MgO‐NiO, A1 2 O 3 ‐Y, O 3 , NiO‐Cr 2 O 3 , and NiO‐Al 2 O 3 . Electron beam spreading within the specimen was incorporated into a model to quantitatively measure solute segregation. Grain‐boundary segregation occurred in A1 2 O 3 ‐Y 2 O 3 and NiO‐Cr 2 O 3 but was not detected in MgO‐NiO and NiO‐Al 2 O 3 specimens. These results and the quantitative measurements agree with equilibrium solute segregation theories. Microhard‐ness measurements indicate no difference in hardness between the grain boundary and the matrix for Cr‐doped NiO, a system in which segregation was detected.