Abstract
In the ceramics of SiC and AlN, heat transfer is dominated by phonon transport. The phonon mean free path is influenced by microstructures of the ceramics. Accordingly, the thermal conductivity is closely related to the microstructures (pores, grain-boundary phase, defect, impurities, etc). The pore in the ceramic is an important factor for the thermal conductivity. In the AlN ceramic, oxygen is the most deleterious impurity and the oxygen-related defects in the grain affect strongly the thermal conductivity. The grain-boundary phases (amount, composition, structure, etc) also affect the thermal conductivity. On the other hand, the thermal conductivity is not so influenced by the grain size because the phonon mean free path is a few tens nm at room temperature. The microstructural information is useful to enhancement of the thermal conductivity of the ceramics.
