Impurity Distribution in MgO

Microprobe studies were conducted on hot‐pressed polycrystalline MgO compacts, nominally 99.5 and 99.95% pure. Results indicated that in MgO some common impurities, such as Al, Ca, and Si, when present in amounts as small as 30 atomic ppm, were segregated to grain boundaries. Mutually incompatible segregated phases existed at grain boundaries. Other impurities such as Fe appeared to be uniformly distributed. Although some impurity agglomeration was noted, it was not required for impurity segregation. The presence of such agglomerates would complicate the problems of chemical analysis.