Thermal conductivity of single crystal and ceramic AlN

We have applied the Callaway theory and used a detailed account of three-phonon scattering processes to calculate the thermal conductivity of three AlN single crystal samples containing different amounts of oxygen and two AlN ceramic samples with different grain sizes and oxygen contamination levels. The N-drift contribution to the total conductivity has been quantified. The influence on the thermal conductivity of oxygen-related defects, and grain boundaries in ceramic samples, has been investigated. The theoretical results obtained from this work are in good agreement with available experimental data. Our calculations suggest that the effective boundary length is greater than the reported grain size for each of the two ceramic samples studied by Watari [J. Mater. Res. 17, 2940 (2002)]. (C) 2008 American Institute of Physics.