Study of rare-earth oxide sintering aid systems for AlN ceramics

In the present work, effects of Y2O3 and Dy2O3 sintering aid systems on density and thermal conductivity of AlN ceramics sintered at low temperature were investigated. The AlN powder synthesized by self-propagating high-temperature synthesis (SHS) was mixed individually with six different sintering aids, which were Y2O3, Dy2O3, CaF2–Y2O3, CaF2–Dy2O3, CaF2–Li2CO3–Y2O3 and CaF2–Li2CO3–Dy2O3, and then fabricated by employing press forming technique. The specimens were sintered at 1650 °C in nitrogen atmosphere at atmospheric pressure for 4 h. X-ray diffraction (XRD) was used to identify the secondary phases. The microstructure of the specimen was observed by scanning electron microscopy (SEM). The thermal diffusivity at room temperature was measured by a laser flash technique. Density of sintered specimen was measured by Archimedes displacement method. The result reveals that the density and thermal conductivity of AlN ceramics sintered with one component sintering aids were lower than those of sintered with multiple components sintering aids. The thermal conductivity of AlN ceramics sintered with CaF2–Li2CO3–Y2O3 and CaF2–Dy2O3 were 141 W m−1 K−1 and 142 W m−1 K−1, which were higher than that of any others.