Enhanced mechanical properties of aluminum nitride-yttria ceramics through grain refinement by pressure assisted two-step sintering

Aluminum nitride (AlN) has gained significant attention as a promising ceramic substrate for electronic devices due to their extremely high thermal conductivity and superior electrical resistivity. However, their application is often limited by poor mechanical properties. Here, we employed pressure-assisted two-step sintering to prepare AlN-Y2O3 ceramics, aiming to enhance mechanical performance through grain refinement. Pressure-assisted high-temperature heating at 1680 °C followed by microstructural freezing at lower temperatures led to a significant reduction in grain size from 2.21 µm to 1.08 µm, resulting in improved flexural strength, Vickers hardness, and fracture toughness. Particularly, T2 of 1650 °C has produced a well-balanced performance of mechanical and thermal properties exhibiting a flexural strength of 417 MPa and a thermal conductivity of 144 W/m∙K. These findings provide valuable insights into the development of advanced AlN-Y2O3 ceramics for electronic device applications, while maintaining the composition free from additional reinforcement additives.