Effect of Si3N4 doping and annealing on the thermal conductivity and mechanical properties of AlN ceramics

Abstract

AlN ceramics are widely used in power electronics packaging due to their excellent thermal conductivity. In order to prepare AlN ceramics with good mechanical properties and thermal conductivity, 0–3 wt% Si₃N₄ was doped and annealed at 1600 °C. The effects of Si₃N₄ doping and annealing on the microstructure, thermal conductivity, and mechanical properties of the fabricated AlN ceramics were investigated. The study demonstrated that the incorporation of Si₃N₄ resulted in the generation of Y₂Si₃O₃N₄ and SiAl₄O₂N₄, which not only refined the AlN grains but also enhanced the strength of the grain boundary phase, ultimately enhanced the hardness and fracture toughness of the ceramic samples. Furthermore, the annealing process facilitated AlN grain growth and improved the crystallinity of the grain boundary phase, which increased the thermal conductivity of the AlN ceramics. Notably, after the annealing process, 0.5 SiN samples exhibited a 37% increase in thermal conductivity, and a concurrent 30% increase in fracture toughness and a 23% increase in hardness, reaching 4.2 MPa·m^1/2 and 12.8 GPa, respectively. Finally, this study explores the mechanism of Si₃N₄ doping in order to modulate the properties of AlN ceramics by changing the liquid phase composition.