Mg Distributions at Grain Boundaries in Sintered Alumina Containing MgA1 2 O 4 Precipitates

It is demonstrated that spinel (MgAI 2 O 4 ) grain‐boundary precipitates in A1 2 O 3 doped with 0.1 wt% MgO can be misinterpreted as solute segregation when analyzed with surface‐sensitive techniques which lack adequate spatial resolution. Further, it is shown that since Mg is preferentially removed during the inert‐ion sputter etching of MgAI 2 O 4 , Mg composition vs depth profiles obtained with sputtering from alumina surfaces containing spinel precipitates are not a valid measure of the Mg distribution.