Effects of Li2O on the low temperature sintering and thermal conductivity of AlN ceramics

The effect of Li2O on the densification and thermal conductivity of AlN ceramics sintered at low temperature were studied using Li2CO3, CaF2 and Y2O3 as additives. Liquid formation and changes in phase composition during the sintering were studied by DTA and XRD. The microstructures of AlN specimens sintered at 1650 C were examined by SEM and TEM. The results show that Li2O is an effective sintering aid, leading to high densification and high thermal conductivity at low sintering temperatures. AlN specimens with full densification and thermal conductivity were achieved with Li2O addition. The high densification comes from the promotion of the liquid containing Li and CaYAlO4. The high thermal conductivity is attributed to the purification of the AlN lattice, density enhancement, and the elimination of some grain-boundary phases. 18 refs.