TEM and AES study of microstructure changes during creep of alumina

Transmission electron microscopy (TEM), Auger electron spectroscopy (AES) and scanning electron microscopy (SEM) were used for the study of microstructure changes during creep of alumina in the temperature range of 1150-1300 degrees C. TEM revealed a presence of Si and Ca impurities in the intergranular phase between the Al2O3 grains. AES identified a very thin layer of secondary phase with Ca content on the fracture surface of the damaged specimens in the areas where microcrack formation between grains caused the failure. SEM revealed a cavity/micro-crack formation between the grains during the creep process on the tensile surface of the sample stressed in bending mode. Based on the detailed analysis, it seems that the main creep controlling mechanism in the studied material is cavity/microcrack formation influenced by the presence of impurities.