Influence of grain size and grain edge phase on the flexural strength of aluminum nitride ceramics with Y2O3 sintering additive

The necessity for efficient heat dissipation compels AlN packaging materials towards a thinner profile. In response to the ensuing concerns regarding the reliability of strength, the effects of the grain edge phases and grain size on flexural strength are investigated in this study. Different preparation processes, including (hotpressed sintering, pressureless sintering, and annealing) are employed to prepare AlN ceramics with different grain edge phases and grain sizes. After classifying the morphology of the grain edge phases and fitting the HallPetch relationship, it is found that the grain edge phases had a more significant influence on the flexural strength. Depending on the morphology, the negative effects can be divided into three degrees. While the finer grain size proves advantageous for the flexural strength. Consequently, in the non-additive system, the flexural strength of AlN ceramic is 422 MPa, with an average grain size of 8.47 mu m. For the additive-doped system, the maximum flexural strength can reach 532 MPa, which can be attributed to the limited average grain size resulting from the hot-pressed sintering process, approximately 1.32 mu m. These results could potentially be employed in the microstructural design of high-strength AlN ceramics.