Abstract
It is important to investigate lattice defect structure in AlN crystal to improve the properties of AlN ceramics. Positron annihilation lifetime measurement (PAL) was carried out to investigate lattice defects in high thermal conductivity AlN ceramics. PAL measurement can detect atomic vacancy type defects like point defect in crystal with non-destruction and high sensitivity. Two positron lifetime components were observed at 230 and 132 ps, which were assigned to lifetime components of aluminum-site vacancy (VAl) and AlN perfect crystal, respectively. There was a good correlation between positron mean lifetime and thermal conductivity of AlN ceramics. Also, it was found that there was a good agreement between VAl concentration calculated from thermal conductivity and positron lifetime analysis. On the other hand, VAl concentration calculated from dissolved oxygen concentration in AlN grain was two orders higher. It was suggested that aluminum octahedrally coordinated to oxygen structure formed below 0.75 at% and they were not affect to phonon scattering.
