Low-temperature fabrication of Si3N4 ceramics with high thermal conductivities using a single Mg2Si sintering additive.

Silicon nitride ceramics were prepared by plasma-activated sintering at 1550 °C with 2−5 wt% Mg 2 Si as a sintering agent. The effects of the Mg 2 Si content on the phase, microstructure, and thermal conductivity of the ceramics were studied. Mg 2 Si reacts with SiO 2 to form MgO and Si, benefiting to the transformation and densification of Si 3 N 4. After heat treatment at 1700 °C for 6 h in a flowing N 2 , the residue Si reacted with N 2 and lattice O to form Si 3 N 4 and SiO, resulting in decreases in the grain-boundary phase and lattice O content. After the heat treatment, the sample prepared with 3 wt% Mg 2 Si achieved a relatively good balance between the thermal conductivity and strength, with values of 110 W/(m⋅K) and 705 ± 30 MPa, respectively. [ABSTRACT FROM AUTHOR]