Role of additives in enhancing the thermal conductivity of AlN ceramics

The thermal conductivity of AlN ceramics with different amounts of Y(2)O(3) as sintering additive has been calculated at low, intermediate and high temperatures by applying the Callaway theory and using a detailed account of three-phonon scattering processes. By making a quantitative analysis of the results, it is found that the increase in the room-temperature conductivity due to the addition of Y(2)O(3) is largely attributed to the decrease in the oxygen impurities level in the AlN crystal. In addition to matching the experimental measurements (available in a limited temperature range) our theoretical work predicts the resulting thermal conductivity over a large temperature range.