Effect of Additive Size on the Densification and Thermal Conductivity of AlN Ceramics with MgO–CaO–Al 2 O 3 –SiO 2 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℃. AlN exhibits higher sinterability with nano-MCAS than with micro-MCAS, and both specimens approach their maximum densities when sintered at 1600℃ for 4 h. The thermal conductivities of AlN with 5 wt% of nano- and micro-MCAS additives sintered at 1600℃ 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.