β-Si₃N₄結晶モフォロジーの制御とそのメカニズム (第2報)

ランタノイド焼結助剤の効果

抄録

Alpha-Si₃N₄ powder mixed with SiO₂ and Ln₂O₃ (Ln=La, Gd or Yb) was heat-treated at 1750-1900°C. After removing the glassy phase, the morphologies of β-Si₃N₄ crystals were quantitatively analyzed. The aspect ratios of β-Si₃N₄ crystals doped with different lanthanide oxides increased in the order of La₂O₃>Gd₂O₃>Yb₂O₃ at high annealing temperatures. The anisotropic Ostwald ripening model successfully simulated grain growth behaviors of β-Si₃N₄ with different lanthanide additives, and suggested that the observed difference in grain growth behaviors be due to the change in the reaction rate at the (100) interface between the β-Si₃N₄ crystal and the Ln-Si-O-N liquid phase.