SINTERING BEHAVIOR OF FINE ALUMINUM NITRIDE POWDER SYNTHESIZED FROM ALUMINUM POLYNUCLEAR COMPLEXES

The sintering behavior of fine AlN powder synthesized from an aluminum polynuclear complex was investigated. The focus of this work was to investigate the densification behavior of the AlN powder with different particle sizes (specific surface area: 3.2-22.8 m2/g). The AlN powder was synthesized from basic aluminum chloride and glucose mixed in a water solution. This powder was divided into two groups: one with 2 wt% Y2O3 added as the sintering aid and the other without such an additive. The AlN powder investigated possessed favorable densification potential. The density of the AlN powder with a surface area of 16.6 m2/g and without additives attained theoretical density at 1700-degrees-C. Adding Y2O3 further decreased the sintering temperature required for full densification to 1600-degrees-C. It is speculated that low-temperature sintering of our fine AlN powder with Y2O3 Proceeds in two steps: in the initial stage, sintering proceeds predominantly through interdiffusion between yttrium aluminates formed on the AlN powder surface; in the second stage, the densification may occur by the interdiffusion between solid phases formed by a reaction between the yttrium aluminates and AlN. To investigate the effect of oxygen on sintering, the content of oxygen in AlN powder was varied while the particle size was kept constant. In this study, the difference in surface oxygen content scarcely affected the sintering behavior of fine AlN powder.