Improved thermal conductivity of β‐Si ₃ N ₄ ceramics by lowering SiO ₂ /Y ₂ O ₃ ratio using YH ₂ as sintering additive

A two‐step sintering process was conducted to produce β‐Si 3 N 4 ceramics with high thermal conductivity. During the first step, native SiO 2 was eliminated, and Y 2 O 3 was in situ generated by a metal hydride reduction process, resulting in a high Y 2 O 3 /SiO 2 ratio. The substitution YH 2 for Y 2 O 3 endow Si 3 N 4 ceramics with an increase of 29% in thermal conductivity from 95.3 to 123 W m −1 K −1 after sintered at 1900°C for 12 hours despite an inferior sinterability. This was primarily attributed to the purified enlarged grains, devitrified grain boundary phase, and reduced lattice oxygen content in the YH 2 ‐MgO‐doped material.