Effects of Grain Sizes and Impurities on Thermal Conductivity in Aluminum Nitride

Abstract

The effects of grain sizes and oxygen impurities on thermal conductivity in aluminum nitride (AlN) ceramics has been calculated by density functional perturbation theory (DFPT) and quasi-harmonic approximation (QHA) combined with Debye theory in the paper. From 300K up to 1000K, the predicted thermal properties are compared with experimental data. The agreements with experiment suggest that the theoretical method used in the paper is an effective approach. From our theoretical study, the reduction of thermal conductivity is greater between grain sizes of 1μm and 5μm, while it’s smaller between 8μm and 10μm. Oxygen defects bring about greater influence on thermal conductivity at low temperature than at high temperature. The influence of the oxygen defect is not as significant as the grain sizes when the oxygen concentrations are less than 0.70 at. %, so it’s more important to increase the grain sizes than reduce the oxygen contents in the preparation process to achieve high thermal conductivity AlN ceramics.