Electronic structures, elastic properties, and minimum thermal conductivities of cermet M sub(3)AlN

The electronic structures and elastic anisotropies of cubic Ti sub(3)AlN, Zr sub(3)AlN, and Hf sub(3)AlN are investigated by pseudopotential plane-wave method based on density functional theory. At the Fermi level, the electronic structures of these compounds are successive with no energy gap between conduct and valence bands, and exhibit metallicity in ground states. In valence band of each partial density of states, the different orbital electrons indicate interaction of corresponding atoms. In addition, the anisotropy of Hf sub(3)AlN is found to be significantly different from that of Ti sub(3)AlN and Zr sub(3)AlN, which involve the differences in the bonding strength. It is notable that Hf sub(3)AlN is a desired thermal barrier material with the lowest thermal conductivity at high temperature among the three compounds.