Effect of Additive Size on the Densification and Thermal Conductivity of AlN Ceramics with MgO–CaO–Al2O3–SiO2 Additives

In this study, we investigate the effect of additive size on the densification and thermal conductivity of AlN ceramics with MgO-CaO-Al2O3-SiO2 (MCAS) additives. Micro-sized MCAS powder prepared via melting and nano-sized MCAS powder synthesized via the polymeric complex method are used as sintering additives. We analyze the densification behavior of AlN added with 5 wt.% of MCAS by dilatometry as well as by isothermal sintering in the temperature range of 1300 ~ 1700°C. AlN exhibits higher sinterability with nano-MCAS than with micro-MCAS, and both specimens approach their maximum densities when sintered at 1600°C for 4 h. The thermal conductivities of AlN with 5 wt% of nano- and micro-MCAS additives sintered at 1600°C are 82.6 and 32.0 W/mK, respectively. We find that nano-MCAS is more effective in sintering of AlN ceramics at lower temperatures, and thus for enhancing their thermal conductivities. Key words: AlN, Sintering additive, Densification, Thermal property