Analysis of trace amounts of emitted gases during fracture of high-purity alumina under ultrahigh vacuum-Effects of sintering atmosphere and sintering time on gas emission behavior

The effects of sintering atmosphere and sintering time on gas emission behavior during fracture of high-purity Al₂O₃ were investigated under ultrahigh vacuum using a mass spectrometer to examine the behavior of gases in the material. The gas in the sintering atmosphere was predominantly emitted at the moment of fracture for all specimens. The total amount of gas emitted from a specimen sintered in O₂ was less than that of a specimen sintered in air or Ar, showing that the mobility of O₂ in the material was much higher than that of N₂ or Ar. During prolonged sintering, the density of specimens decreased, while the amount of emitted gas increased. Entrapped gases in the sintered body were concluded to bring about the density decrease during grain growth.