Abstract
A plasma etching technique was applied to make samples for a precise chemical analysis of grain boundary phases in Si3N4 ceramics by means of analytical transmission electron microscopy (TEM). After the plasma etching using CF4+7.8%O2 gases, the matrix grains of Si3N4 were selectively removed and the grain boundary phases remained. This sample was used to investigate chemical composition in grain boundary triple points. The triple points were composed of an SiO2-rich phase near the Si3N4 grains and additives of Y and Nd were enriched at the center. The mechanism of the selective etching of CF4+O2 plasma is discussed.